Chuyen de Huu Co HSG THPT

Chuyn bi dng HSG Ha hu c

CHNG I: AMIN V MUI IAZONI Bi: AMIN I.KHI NIM 1.nh ngha Amin l dn xut th H ca NH3, bng cc gc hirocacbon bo hay thm. Amin loi bo: gc hirocacbon l gc ankyl hay xicloankyl CH3-CH2CH2-NH2 Amin thm, gc hyrocacbon l nhn thm:

NH22.Bc amin: Amin bc 1, c nhm chc amin -NH2 nh vi 1 gc hirocacbon Amin bc 2, c nhm chc amin NH nh vi hai gc hirocacbon Amin bc 3, N nh vi 3 gc hirocacbon RNH2 (CH3)2CNH2 R2NH CH3CH2NHCH3 R3N (CH3)3N amin bc nht amin bc hai amin bc ba II.DANH PHP Amin thng c gi theo tn thng thng hn l IUPAC Tn gc hirocacbon+amin (vit lin 1 ch) CH3NH2 (CH3)2NH (CH2CH2CH2)3N CH3CH2CH-NH2CH3

X-amino + tn hirocacbon Tn IUPAC aminometan N-metylaminometan N,N-ipropylaminopropan Amino-2-butan N, N-etylmetylamino-2-butan

Tn thng thng metylamin imetylamin tri-n-propylamin sec-butylamin metyletyl-sec-butylamin

CH3CH2CH - N - CH2CH3 CH3 CH3

NH2 N(CH3)2 H3C NH2

phenylamin,anilin

aminobenzen(benzenamin)

imetylphenylamin imetylanilin p-toluiin

N, N-imetylbenzenamin N, N-imetylanilin p-aminotoluen

III.PHNG PHP TNG HP 1. Ankyl ha trc tip amoniac hay amin NH3 tc dng vi RX to thnh mui: 1Trng THPT chuyn Tn Ph- nh Qun

Chuyn bi dng HSG Ha hu cO CH3CH2-Br + NH3 CH3CH2NH3+Br- N aH CH3CH2NH2 2.Phn ng kh a, Kh hp cht nitro Nhm nitro b kh thnh amin bc nht. Phn ng ch yu dng iu ch amin thm. Tc nhn kh c th l hiro ha xc tc hay tc nhn kh ha hc trong dung dch. CH3 CH3 NO2 NH2 [H] p, to CH3 CH3 Fe o C2H5OH, HCl, t NH CH(CH3)NO2 CH(CH3)2 2 2

NH2 NO2 b,Kh hp cht nitrin Nitrin b kh bng hiro trn xc tc hoc bng LiAlH4 trong dung dch to thnh amin bc nht: H2/Ni R-CN R-CH2-NH2 hay LiAlH4 IV.CU TRC Amin l sn phm th ca NH3, nn ni chung c cu trc ging cu trc ca NH3: NH3 R-NH2 R-NH-R R-N-R | R V.TNH CHT HA HC 1. Tnh baz Amin l baz Lewis do amin c cp electron n khng lin kt N tng t nh ancol, ete. Khi xt mt amin c tnh baz, cn so snh tnh n nh ca amin so vi mui amoni. Nu ion amoni n nh hn amin th amin c tnh baz. Khi so snh tnh baz ca amin bo, cn ch hai nhn t: nhn t phn cc v nhn t solvat ha. Nu xt theo nhn t phn cc, khi tng gc R s lm tng mt electron N, va lm tng kh nng kt hp proton, va lm tng tnh n nh ca ion amoni. Do tnh baz gim theo th t: R3N > R2NH > RNH2 Nu xt theo nhn t solvat ha ca ion amoni, s lng proton ion amoni cng nhiu th kh nng solvat ha ca ion cng ln, do , tnh baz thay i theo th t: RNH3+ > R2NH+2 > R3NH+ Tng hp c hai nhn t trn, s thay i tnh baz ca cc amin c bc khc nhau nh sau: RNH2 < R2NH > R3N Tnh baz ca cc amin thm bo cng thay i theo th t nh trn:

NH2

NR2

2. S to mui Do c tnh baz, amin c kh nng to mui vi axit: C6H5NH3+ClC6H5NH2 + HCl (CH3)2NH2+ .NO3(CH3)2NH + HNO3 C6H5N(CH3)2 + RCOOH C6H5NH+(CH3)2.RCOO2Trng THPT chuyn Tn Ph- nh Qun


Cc ion amoni c kh nng tan tt trong nc hn l amin: CH3(CH2)9NH3+NH3+ClCH3(CH2)9NH2 + HCl ( khng tan) (tan tt) 3.Phn ng ca hir ca N-H 3.1. Phn ng ankyl ha Hiro nh vi N c th b th bi gc hirocacbon khi amin tng tc vi halogenua ankyl bc 1, 2, 3 hay thm. Nu ankyl ha hon ton th thu c mui amoni bc 4: RX RX RX RNH2 RRNH RR2N [RR3N]+XMui amoni bc 4 l hp cht inoic, c nhit nng chy cao v d tan trong nc Ch : Cc dn xut thn ch tham gia phn ng khi c nhm ht electron v tr ortho v pa ra, th d nh 2, 4-(NO2)C6H3F 3.2. Phn ng axyl ha Amin bc nht v amin bc hai phn ng vi halogenua axit hay anhirit axit to thnh amit: 2CH3NH2 + CH3COCl CH3NH-CO-CH3 + CH3NH3+ClCH3NH2 + (CH3CO)2O CH2NH-COCH3 + CH3COOH + Tng qut: R - NH2 + Cl - CO - R cngtach R - NH - COR + HCl cngtach + R - NH2 + RCOO - CO - R R - NH - COR + RCOOH Nu dng clorua axit th cn 1 lng tng ng trung ha axit clohiric to thnh. ng dng: bo v nhm -NH2 trong tng hp hu c Nh phn ng axetyl ho (dng axetyl clorua hoc anhirit axetic ngi ta bo v nhm amino trong tng hp hu c ). bo v nhm amino ca aminoaxit v peptit trong qua trnh tng hp peptit, khng dng phn ng axetyl ho c, v khi mun gii phng nhm -NH2 ra khi -NHCOCH3 phi thu phn, do lm t lun c lin kt peptit - CO - NH -. Tt hn ht nn dng C 6H5CH2OCOCl (benzyl oxicacbonyl clorua) v khi cn gii phng nhm - NH2 c th dng phn ng kh bng H2/Pd (khng nh hng ti lin kt peptit). Th d tng hp ipeptit Ala-Gly theo s : C6H5CH2OCO HNCH(CH3)-COOH C H CH OCOCl + H2NCH(CH3)-COOH6 5 2

H2NCH2COOCH2C6H5 C6H5CH2OCO HNCH(CH3)-CO HNCH2COOCH2C6H5 DDC H2/Pd/C 2 C6H5CH3 + CO2 + H2NCH(CH3)-CO HNCH2COOCH2C6H5 (DCC: ixiclohexylcacboiimit). 3.3. Phn ng vi axit nitr: Axit nitr HONO gn nh khng tc dng vi amin bc 3, tr phn ng nitroso ho nhn thm. Axit nitr tc dng vi amin bc hai sinh ra nitrosoamin(N - nitrosoamin) c mu vng, nh vy c th phn bit amin bc hai vi amin cc bc kh. Th d: (C2H5)2NH + HONO H (C2H5)2N N = O + H2O (Cht lng mu vng) (+ ) Amin bc mt tc dng HONO sinh ra mui iazoni RN NX(-) (t RNH2) hoc(+ )

ArN NX(-) (t ArNH2). C ch phn ng ca amin bc mt tng t trng hp amin bc hai ch lc u cng to ra hp cht nitroso, sau phn ng tip nh sau:R- NH - N = O H + R- NH = NOH -H + R - N = NOH(+ )

(+ )

H

+

+ R - N = NOH2

R-N

N

3Trng THPT chuyn Tn Ph- nh Qun


ng ch l mui iazoni dy bo RN N khng bn nn chuyn ho ngay thnh ancol gii phong kh nit. Trong khi y, mui iazoni dy thm li bn nhit thp v ch phn hu thnh phenol ng thi gii phng N2 khi un nng. Th d: OH2 NaNO2 + N2 + C2H5OH + HCl C2H5 - NH2 NCl C2H5 - N HCl, 00C

C6H5 - NH2

NaNO2 HCl, 00C

C6H5 - N

+

NCl

OH2 un

N2 + C6H5OH +

HCl

Mui iazoni thm ArN2(+)X(-) c dng rng ri trong tng hp hu c. 3.4. Phn ng th nhn thm: Cc nhm -NH2, -NHR v - NR2 (R = ankyl) u hot ho nhn thm v nh hng ortho para. a, Halogen ho Nc brom d dng phn ng vi anilin cho 2, 4, 6 - tribromoannilin (kt ta trng), vi p toluidin p - CH3C6H4NH2 cho 2,6 - ibrom - 4 - metylanilin. Brom lng tc dng vo v tr para ca N - axetylanilin (hay axetanilit) C 6H5NH COCH3; thu phn sn phm sinh ra s c p - bromanilin. Iot trong hn hp vi NaHCO3 ( trung ho HI sinh ra trong phn ng) tc dng vi anilin cho ta p - Iotanilin. b, Nitro ho Khng th trc tip nitro ho anilin bng HNO 3, v khi y amin b proton ho tr thnh mui amoni; nhm - N H 3 sinh ra s phn hot ho rt mnh v nh hng th vo v tr meta, mun mononitro ho anilin phi bo v nhm - NH2 ri mi nitro ho, sau gii phng - NH2. NH2 NH2 NHCOCH3 NHCOCH3(CH3CO)2O HNO3, H2SO4 1) H3O+ 2) OHNO2 NO2NHCOCH3 HNO3, H2SO4(+)

Nu mun a nhm nitr vo v tr ortho phi kho v tr para ri mi nitro ho:NH2 (CH3CO)2O NHCOCH3 H2SO4 NHCOCH3 HNO3, H2SO4

SO3H NHCOCH3 NO2 H2SO4 OH2 SO3H

SO3H NHCOCH3 NO2



Bi: MUI IAZONII.CU TRC CA CATION IAZONI Ion iazoni c nhm N2 hay NN mang in tch dng phn b trn c hai nit nhng tp trung N nh vi phn t benzen nhiu hn: + (Ar-N2)

N

+ N hay

+ N

N

trong h lin hp, mt lin kt lin hp c vi h ca nhn benzen cn mt lin kt nm thng gc vi mt phng ny II.TNH CHT HA HC Mui iazoni thm ArN2(+)X(-) c th ng vai tr l cht phn ng trong cc phn ng thay th nhm - N2(+), mt khc c th l tc nhn electrophin tham gia phn ng th electrophin nhn thm, l phn ng ghp. 1. Phn ng th nhm -N2(+) 1.1. Th -N2(+) bng -OH v bng -I -N2 + Y Ar+ Ar - Y N Ar - N (+) (-) Khi un nng dung dch ArN2 , H2SO4 trong nc s sinh ra ArOH theo c ch nu trn (H2SO4(-) c tnh nucleophin km H2O). Phn ng ny c dng tng hp phenol t amin thm. Th d:m - NO2C6H4NH2NaNO2, H2SO4, H2O

+ m - NO2C6H4N2HSO4

OH2 t0

m - NO2C6H4OH +

N2

Khc vi H2SO4(-) c tnh nucleophin km nc, anion I(-) c tnh nucleophin cao hn nc nhiu, nn d tc dng vi mui iazoni sinh ra ArI. Th d: KI + NaNO2, HCl C6H5I C6H5NH2 C6H5N2Cl 0C 0C 25 0-5 (+) 1.2.Th -N2 bng - Cl, -Br v -CN (phn ng Sandmeyer) Nh tng git huyn ph ca Cu2X2 (X = Cl, Br hoc CN) vo dung dch ArN2(+)X(-) lnh s xy ra phn ng th -N2(+) bng -X. Th d: KI + NaNO2, HCl C6H5I C6H5NH2 C6H5N2Cl 0C 250C 0-5 + NaNO2, HBr Cu2Cl2 o-ClC6H4Br o-ClC6H4NH2 o-ClC6H4N2Br 0 - 50C Cu(CN)2 + NaNO2, HCl p-CH3C6H4CN p-CH3C6H4N2Cl p-CH3C6H4NH2 0 - 50C (+) 1.3. Th -N2 bg -F v -NO2 Sau khi iu ch mui areniazoni tetrafluoroborat ArN2(+) BF4(-) em nhit phn s c ArF hoc cho tc dng vi NaNO2/Cu s c ArNO2. Th d: 5Trng THPT chuyn Tn Ph- nh Qun


p-NO2C6H4NH2

+ NaNO2 p-NO2C6H4N2BF4 HBF4 to-N2, -BF3NaNO2/Cu

p-NO2C6H4F

p-(NO2)2C6H4

1.4. Th -N2(+) bng -H. Phn ng kh: Dng axit hipophotphor(H3PO2) hoc etanol c th kh c mui iazoni ArN2(+) thnh ArH: + H3PO2 NaNO2, H + ArNH2 ArH ArN2 ho C2H5OH c 0 - 50C Nh phn ng ny ngi ta c th loi b nhm amino trong vng thm v do tng hp c nhng dn xut th khng th iu ch bng phn ng th trc tip. Th d t toluen tng hp m - bromotoluen: CH3 HNO3 CH3Sn, HCl

CH3(CH3CO)2O

CH3 Br2 NHCOCH3 CH3 CH3H3PO2

NO2 CH3 OH2 xt Br NHCOCH3 NH2 CH3

NH2

NaNO2 Br HCl Br N2(+)Cl-

-H3PO3

Br

2. Phn ng ghp: Ion arenddiazoni ArN2(+) l nhng tc nhn electrophin khng mnh, thng ch tc dng vi nhng cht thm giu mt electron nh amin, phenol,...theo c ch electronphinin: S 2 + E R-N N + H R-N=N Y Y Cu t iazo Cu t azo Hp cht azo 2.1.Phenol v dn xut Nu cu t azo l phenol, phn ng ghp xy ra v tr para v pH ti u l 9 - 10 (+ ) chuyn -OH thnh -O(-) c hiu ng +C mnh hn. pH cao hn ArN N s chuyn thnh ArN = NOH v Ar - N = N-O(-) khng cn tnh electrophin. Th d: S 2 + (-) (-) E C6H5 - N N + C6H5-N=N O O 2.2.Amin thm 6Trng THPT chuyn Tn Ph- nh Qun


Nu cu t azo l amin thm bc 3 nh C6H5 - NR2pH thun li l 5-9, phn ng cng xy ra v tr para. Th d:C6H4-N N ++

N(CH3)2+

C6H5-N=N

N(CH3)2

Phn ng mui iazoni vi amin thm bc mt xy ra nguyn t nit. Th d:C6H5 - N N + H2N - C6H5 C6H5-N=N - NH - C6H5

i vi amin thm bc hai nh C6H5NHCH3 phn ng xy ra c nit ln v tr para ca vng thm. Th d:

C6H5 - N

+

C6H5 - N=N N + NHCH3 C6H5 - N=N - N(CH3)2

NHCH3



CHNG II: AMINOAXIT - PROTIT Bi: AMINOAXITI. NH NGHA-CU TRC - DANH PHP 1.nh ngha: Aminoaxit l cc HCHC tp chc, phn t c cha ng thi nhm chc -NH2 (amino) v -COOH (-cacboxyl) 2.Cng thc tng qut: CT chung: (NH2)x R (COOH)y x = y hoc x > y hoc y > x Khi x=1, y= 1, R: no, mch h th CT l NH2 - CnH2n - COOH VD: C3H7O2N ng phn aa?(2 p) 3.Cu trc: a s cc aa thin nhin l cc , dy L trng thi rn tn ti ion lng cc, trong dung dch tn ti dng cn bng V d 1: Cu hnh R/S v D/L ca hu ht cc amino axit l g ? (b) Vit cu hnh tuyt i ca (i) Lcystein v (ii) L-serin. (a) S v LCOO H3N H CH2SH H3N COO H CH2OH

(b)

(i)

(ii)

V d: (a) Vit tt c cc ng phn lp th ca threonin (dng cng thc Fischer). (b) Xc nh L-threonin v cho bit danh php R/S ca n.(a)H3N+ H CH3 COOH OH H HO CH3 COO+

COOH3N+ HO CH3 H H H H

COO+

NH3 H

NH3

OH CH3

racemat-1 (threo)

racemat-2 (erythro)

(b) Cc cu hnh tng ng vi racemat-1 l L- v D-threonin, vi racemat-2 l L- v D allothreonin, L- c xc nh theo cu hnh ca C . Nu c mt C bt i trong nhm R, cu hnh ca n khng lin quan n k hiu D,L hay R,S ca amino axit. L-threonin l (2S,3R). ng phn lp th dia - (2S,3S)-threonin- c gi l L-allothreonin

4.Danh php:a,Tn thng: Axit +K hiu v tr (-NH2) [ ( , , , ...)]+ amino + tn thng thng ca axit tng ng b,Tn quc t: Axit+v tr nhm -NH2 +amino+tn quc t ca axit HC.



5.Tnh axit , baz ca aaTn Glixin Alanin Valin* Leuxin* Isoleuxin* Serin Threonin* Axit aspatic Asparagin Axit glutamic Glutamin Lysin* Hydroxylizin Arginin* Systein Cystin Methionin* Phenylalanin Tyrosin*

K hiu Gly Ala Val Leu ILeu Ser Thr Asp Asp(NH2) Glu Glu(NH2) Lys Hylys Arg CySH CySSCy Met Phe Tyr

Cng thc Monoaminomonocacboxylic H3N+CH2COOH3N+CH(CH3)COOH3N+CH(i-Pr)COOH3N+CH(i-Bu)COOH3N+CH(s-Bu)COOH3N+CH(CH2OH)COOH3N+CH(CHOHCH3)COOMonoaminodicacboxylic v dn xut amit HOOC-CH2-CH(+NH3)COOH2NOC-CH2-CH(+NH3)COOHOOC-(CH2)2-CH(+NH3)COOH2NOC-(CH2)2-CH(+NH3)COODiaminomonocacboxylic H3N+-(CH2)4-CH(NH2)COOH3N+-CH2-CHOH-CH2-CH2-CH(NH2)COOH2N+=C(NH2)-NH-(CH2)3-CH(NH2)COOAminoaxit cha lu hunh H3N+CH(CH2SH)COO-

OOC-CH(+NH3)CH2S-SCH2CH(+NH3)COO-

CH3SCH2CH2CH(+NH3)COOAminoaxit thm PhCH2CH(+NH3)COOp-C6H4CH2CH(+NH3)COOAminoaxit d vngCH2 CH COO + NH3

Histidin*

His

HN

N Prolin Pro

HHydroxyprolin Hypro

N

H COO-

H H N H COOHCH2 CH COO +NH3

HO H

Tryptophan*

TryN H



II. Tnh cht vt l: Cht rn, khng mu, a s tan tt, c nhit nc tng i cao. III. Tnh cht ho hc: 1. Tnh cht axit-baz: im ng inTnh lng tnh OH+ H3N+CHRCOOH cation A (+1)

tnhbaz

H3N+CHRCOO- + H2O ion lng tnh B (0)

tnhaxit

H2NCHRCOOanion C (-1)

+

H3O+

Gi tr pH m ti phn t aminoaxit tn ti dng ion lng cc (I) cn bng v in tch v khng di chuyn v mt in cc no c c gi l im ng in v k hiu l pH1. Gi tr v im ng in ca cc aminoaxit thin nhin c gii thiu bng 17.1. im ng in ca cc axit monoaminomonocacboxylic tnh c theo biu thc: pK a1 + pK a2 pH 1 = 2 Gi tr pKa1 ng vi nhm -COOH, pKa2 ng vi nhm N H 3 . V d i vi glyxin, pKa1 = 9,6 tnh c pH1 = (2,34 + 9,6) : 2 = 5,97. Cc aminoaxit c gi tr pH1 khc nhau nn mt gi tr pH xc nh cc aminoaxit s dch chuyn v catot hoc anot vi nhng vn tc khc nhau. Da vo c tnh ny ngi ta xy dng phng php in di phn tch aminoaxit t hn hp ca chng. 2. Tnh cht ca nhm cacboxyl: a, Phn ng este ho: Tng t axit cacboxylic, aminoaxit phn ng vi ancol c axit v c xc tc cho este ( dnh mui). V d: + + bo ha kh HCl H3N - CH(R) - COO + C2H5OH H3N - CH(R) - COOC2H5 Cl + OH2 Ra sn phm bng dung dch NH3 s thu c este: H2N - CH(R) - COOC2H5. b, Phn ng ecacbolxyl ho: Phn ng tch CO2 t nhm cacboxyl xy ra trong c th nh enzim ecacboxyllaza: za H2N - CH(R) - COOH decaboxyla R - CH2 - NH2 + CO2 3. Tnh cht ca nhm amino: a, Phn ng vi axit nitr HNO2 Tng t cc amin bc mt, aminoaxit phnu ng vi axit nitr gii phng ra N2 v to thnh hiroxiaxxit: H 3 N CH ( R ) CO O + HONO HO CH ( R ) COOH + N 2 + H 2 O Da vo th tch N2 thot ra c th tnh c lng aminoaxit trong dung dch. b, Phn ng eamino ho (tch nhm amino) Phn ng xy ra trong c th nh enzim, aminoaxit chuyn thnh xetoaxit v NH3. V d: O], CH3 - CH(NH2) - COOH [enzim CH3 - C - COOH + NH3 O Alamin Axit piruvic 10Trng THPT chuyn Tn Ph- nh Qun+ +


c, Phn ng ankyl ho hoc aryl ho Nhm amino ca aminoaxit c ankyl ho hoc aryl ho bng dn xut halogen to ra dn xut N-ankyl hoc N - aryl tng ng. V d : H + + CH3I + H3N - CH2 - COO H3C N CH2-COO + HI HO2N

+ F + H3N - CH2 - COONO2

O2N

NH-CH2-COOH NO2

+ HF

N-(2,4-dinitrophenyl) glyxin

d, Phn ng axyl ho: Nhm amino ca phn t aminoaxit c axyl ho dng bi halogenua axit trong mi trng kim. Vd: + - 1) OH-/H2O C6H5 - C - NH(R) - COOH + HCl C6H5 - C - Cl + H3N - CH(R) - COO + 2) H O O Cng c th axyl ha bng anhirit axetic: Cng c th axyl ha bng anhirit axetic: + t0 CH3 - C - NH(R) - COOH + CH3COOH (CH3- CO)2 O + H3N - CH(R) - COOO O e, Phn ng ngng t vi anehit fomic (Phn ng sorenxen) Aminoaxit phn ng d dng vi anehit fomic to thnh dn xut cha nhm metylenamino:

H 3 N CH ( R) CO O + HCH = O CH 2 = N CH ( R) COOH + H 2 O Do nhm amino b kho nn c th chun nhm cacboxyl bng kim. y l phn ng quan trng dng nh lng aminoaxit v nh gi mc thu phn protein. 4. Tnh cht ca c phn t: a, Tc dng ca nhit Cc -aminoaxit (hoc este cachng) khi un nng to thnh iamitvng 6 cnh c gi l ixetopiperazin, do hai phn t aminoaxit b tch hai phn t nc (hoc hai phn t ancol). V d: OO H2C + NH3

+

C O-

+

-

+ H3N-CH2 C=O

t0

H2C HN O

NH CH2 Dixetpiperazin

+

OH2

O



O R-C NH2 C OC2H5 +

O + H2N-CH - R C=O t0 R-CH HN O NH CH-R + C2H5OH

C2H5O

Diankyldixetopiperazin

Tng t cc amit, cc i xetopiperazin b phn hu trong mi trng axit hoc baz, trc ht m vng tao thnh hai phn t aminoaxit: O + + H2O, H H2C NH H3N CH2- C - NH - CH2 - COOH HN CH2 O O (nhm peptit) DipeptitH2O, H + + 2 H3N - CH2 - COO

Khi un nng, ipeptit li khp vng to thnh ixetopiperazin. Cc -aminoaxit b tch NH3 bi nhit to thnh axit , -khng no: + t0 CH2=CH-COOH +NH3 H3N - CH2 - CH2 - COO Cc , va -aminoaxit di tc dng cuat nhit b tch nc to thnh amit vng, thng gi l lactam:CH2 - CH2 - CH2 + NH3 to H2C NH Butirolactam H2 C H2 C

-

O

C=O

C=O

+

OH2

b, Phn ng to hp cht phc Cc -aminoaxit phn ng c vi mt s ion kim loi nng cho hp cht phc kh tan, thng c mu c trng. V d hp cht phc ca glyxin vi Cu2+: O 1 H2N C O - + Cu(OH) CH2 + 2 OH2 2 CH2 - COO 2 Cu H2C 1 + O C NH2 NH3

K ta m xanh t u

O

5. Phn ng mu ca aminoaxit: a, Phn ng vi ninhirin Cc -aminoaxit phn ng vi ninhirin (cn gi l trixeto hirinen hirat) cho sn phm mu tm xanh tan trong nc (ring prolin cho sn phm mu vng):


Chuyn bi dng HSG Ha hu cO OH OH O + R - CH - COOH NH2 O +N inhidrin + NH3 O N O O O tmxanh O H OH + NH3 + CO2 + RCH=O

Phn ng rt nhy, c th pht hin n microgam -aminoaxit, v vy phn ng ny c dng phn tch nh tnh v inh lng cc -aminoaxit. nh lng -aminoaxit c th dng phng php so mu o cng mu dung dch phn ng, hoc dng phng php o th tch CO2. b, Phn ng xangtoproteic Cc aminoaxit c gc hirocacbon thm (Phe, Tyr, Trp...) phn ng vi HNO3 c nng cho sn phm mu vng. c, Phn ng vi thuc th Milon Cc aminoaxit c gc phenol (Tyr...) phn ng vi thuc th Milon (hn hp Hg(NO 3)2 v HNO3 c) khi un nng cho sn phm mu . d, Phn ng Pauli Phn ng Pauli c trng cho tryptophan. Tryptophan phn ng vi axit iazobenzensunfonic trong dung dch kim cho sn phm c mu anh o. e, Phn ng Aamkevic v Hopkin Phn ng c trng cho aminoaxit cha vng inol nh tryptophan. Tryptophan phn ng vi axit gloxilic (O=CH-COOH) c mt H2SO4 c cho sn phm c mu tm. g, Phn ng Sacaguchi Phn ng c cho arginin. Arginin phn ng vi hn hp natri -naphtolat v natri hipobromat cho sn phm mu . IV-IU CH AMINOAXIT 1. Thu phn protein Thu phn protein nh xc tc axit, hoc kim hay enzim thu c hn hp cc L-aminoaxit: H2N-CH RH2N-CH

CO

NH -CH CO - HN-CH R'COOH

CO - ...

H2O/H

R" + H2N-CH CO HN-CH COOH + ....

R" R R' Nh cc phng php thch hp (sc, k, in li...) c th tch ring r tng aminoaxit. 2. Amin ho axit -halogencacboxylic (phong php Peckin) Cho axit -halogencacbylic tc dng vi dung dch amoniac c nhit phng thu c -aminoaxit. H2N-CH COOH + 2 X NH3 H2N-CH COO -

+ NH

+

NH4Br

3

3. Ankyl ho cc este ca axit aminomalonic N-th 13Trng THPT chuyn Tn Ph- nh Qun


Este ca axit aminomolonic N-th (III) c iu ch t ietyl monobrommalonat (I) v kali phtalimiat (II): O BrCH(COOC2H5)2 (I) (II) O + - + N K O N (III) O CH(COOC2H5)2

-KBr

DietylN-phtalimitmalonat ietyl N-phtalimit malonat (III) c ankyl ho bi ankyl halogenua hoc hp cht caconyl , -khng no, sau un nng sn phm ankyl ho trong mi trng axit xy ra qua qu trnh thu phn este v ecacboxyl ho thu c -aminoaxit: O N (III) O H3O+ -CO2 CH(COOC2H5)2 1)Bazo 2) RX O + COOH + C2H5OH O N (III) CR(COOC2H5)2

R-CH - COO + NH3

COOH Phng php ny c dng iu ch nhiu a-aminoaxit, v d methionin, axit glutanic...:O N (III) O CH(COOC2H5)2 1) C2H5ONa 2) H2O/H+ to Me thionin CH3SCH2CH2-CH - COO + NH3

CH3SCH2CH2Cl

1) C2H5ONa

2) CH2=CH-COOC2H5

H2O/H+HOOCCH CH -CH - COO 2 2 to + Axit glutamicNH3

4. Tng hp Streck (Strecker) Cc -aminoaxit cng c tng hp bng cch thu phn cc -aminnonitrin theo s phn ng: + RCH=O +NH3 + HCN + R-CH-N N H2O/H R-CH COO NH2 + NH 3 5. iu ch v -aminoaxit Axit - aminocaproic v axit - aminoenantoic (u khng c trong thin nhin) l nguyn liu quan trng sn xut t capron v t enang. Axit - aminocaproic c iu ch t oxim ca xiclohexanon. Khi un nng oxim ny vi H2SO4 c thu c caprolactam, sau thu phn thnh axit -aminocaproic:



O

H2N-OH OH2

N-OH

H2SO4

c

Oxim ca xiclohexanonH2O/H

C=O H2C NH C C H2 H 2

H2 H2 C C

+

H2N-(CH2)5-COOH

Axit -aminoenantoicc iu ch t etilen v cacbon tetraclorua nh phn ng telome ho to thnh 1, 1, 1, 7 - tetraclohepan, sau thu phn v amin ho: H2O/H2SO4 CCl4 ClCH2-(CH2)5-CCl3 3 CH2=CH2 NH3 ClCH2-(CH2)5-COOH NH2CH2-(CH2)5-COOH

Bi: PEPTITI - Trng thi thin nhin: Mt s cht peptit c trong c th ngi. V d nh trong m c c cacnozin v anserin (u l ipeptit), gan v no c glutation (tripeptit). Glutation cn c trong mm la m v mt s loi nm. Mt s peptit l hormon trong c th sinh vt nh insulin, oxytoxin... II - Cu trc v danh php: 1. Cu trc Peptit thin nhin l hp cht polime ca cc a min oaxit , gm t 2 n khong 50 n v a min oaxit kt hp vi nhau nh cc lin kt peptit. Lin kt peptit

... - HN-CH CO R

NH -CH CO - ... R1

Nhm peptit Tu thuc vo s n v (2, 3, 4, ..., n) aminoaxit trong phn t ngi ta phn chia thnh ipeptit, tripeptit, tetrapeptit...polipeptit. Theo quy c mt peptit c phn t khi trn 10000 c gi l polipeptit; nhng peptit c phn t khi thp hn c gi l oligopeptit. Trong phn t peptit, u mch cha n v aminoaxit cn nhm -NH2 ( +NH3) c gi l u N, cn u mch kia cha n v aminoaxit cn nhm -COOH (hay COO--) c gi l ui C. Theo quy c, u mch c nhm -NH2 c vit pha bn tri, cn u c nhm -COOH c vit pha bn phi: H2N-CH CO NH -CH CO NH - CH COOH R R R Aminoaxit u N Aminoaxit u C Nhm peptit -CO -NH- c cu trc phng, nguyn t H ca nhm -NH- nm v tr anti i nguyn t O ca nhm cacbonyl. Lin kt peptit C-N mang mt phn c im ca lin kt i C=N



Do vy lin kt peptit kh quay t do xung quanh trc C-N, trong khi kh nng quay t do ca cc lin kt n gia C vi nhm peptit l rt ln. l nguyn nhn dn n cu trc xon ca mch polipeptit (xem bi protein). Tng t aminoxit, phn t peptit cng tn ti dng ion lng cc, peptit l hp cht lng tnh. *Tnh axit v baz V d: C mt hn hp protit gm pepsin (pHI = 1,1), hemoglobin (pHI = 6,8) v prolamin (pHI = 12,0). Khi tin hnh in di dung dch protit nu trn pH = 7,0 thi c ba vt cht (xem hnh) Xut pht Cc (+ ) A B C Cho bit mi vt cht c trng cho protit no ? Gii thch. Bi gii :Vt A l pepsin, vt B l hemoglobin v vt C l prolamin. Gii thch : Pepsin l protit c tnh axit mnh (pHI = 1,1) nn tn ti dng anion khi pH =7, di tc dng ca in trng s chuyn v cc dng (anot). Hemoglobin (pHI = 6,8) hu nh tn ti lng cc vi in tch bng khng khi pH = 7, do gn nh khng chuyn dch. Prolamin l protit c tnh baz mnh (pH I = 12,0) nn tn ti dng cation khi pH =7, di tc dng ca in trng s chuyn v cc m (catot). 2. Danh php Tn ca cc peptit c gi theo quy tc sau: - Ghp tn cc aminoaxit to nn phnt peptit theo trt t sp xp ca chng trong mch. - Nhng aminoaxit c nhm cacboxyl tham gia to lin kt peptit c gi tn bng cch i ui in thnh ui yl (xem bi 17.1), aminoaxit ng cui mch cn nhm cacboxyl (ui C) c gi nguyn tn. V d: H2N CH2 CO NH CH(CH3) COOH Glyxylalanin (Gly Ala) H2N CH(CH3) CO NH CH2 COOH Alanyl glyxin (Ala Gly) Cc (-)

H2N CH2 CO NH CH CO NH CH2 COOH Glyxyl phenylalanylglyxin C6H5 CH2 (Gly-Phe-Gly) III- Tnh cht: 1. Tnh cht vt l: Nhng peptit c phn t khi thp l nhng cht kt tinh tan tt trong nc. Cc peptit c phn t khi ln l nhng cht v nh hnh, to thnh dung dch keo vi nc. 2. Tnh cht ho hc: a, Phn ng thu phn: Cc peptit b thu phn hon ton trong dung dch axit nng hoc dung dch kim nng cho sn phm cui cng l hn hp cc aminoaxit. Thng thu phn bng dung dch HCl 2N 1100C trong khong 24 - 72 gi. V d: H+, t0 nH2O CO - ... + H N-CH CO NH -CH CO - HN-CH2

R

R'H2N-CH COOH R

R" + H2N-CH COOH R' + H2N-CH COOH + .... R" 16Trng THPT chuyn Tn Ph- nh Qun


Cc peptit c th c thu phn khng hon ton nhng on peptit ngn hn nh cc enzim c hiu: - Aminoaxit N -u mch c tch ra khi mch nh enzim aminopeptiaza. V d: aminopeptiaza nH2O CO - ... + H2N-CH CO NH -CH CO - HN-CH R R'H2N-CH COOH

R" + H2N-CH CO HN-CH COOH + ....

R" R R' - Aminoaxit C-u mch c tch ra khi mch nh enzim cacboxipeptiaza. cacboxipeptiaza nH2O COOH + ... - HN-CH CO NH -CH CO - HN-CH R R' HN-CH R' R" COOH + H2N-CH COOH R" + ....

... - HN-CH CO R

- phn cch mt s lin kt peptit xc nh trong phn t peptit (hoc protein) c th dng cc enzim proteaza nh tripsin, chimotri-psin, pepsin... . Trpin xc tc cho s phn ct lin kt peptit sau gc lysin hoc arginin. Chimotripsin xc tc cho s phn ct lien kt peptit sau cc gc phenylalanin, tryptophan, tyrosin, leuxin, axit aspactic hoc axit glu tamic. V d: ...-NHCHCO R Enzim Tripsin Chi motripsin Pepsin NHCHCO-... R1 enzim ...-NHCHCOO R + H3NCHCO-... R1

+

Aminoaxit u N Lys, Arg Phe, Trp, Tyr Phe, Trp, Tyr, Leu, Asp, Glu

b, Phn ng vi 2,4 - initroflobenzen: Tng t aminoaxit, nhm -NH2 ca n v aminoaxit N-u mch phn ng c vi 2,4-initroflobenzen cho dn xut 2,4-initro-phenyl (DNP) mu vng :NO2 O2N F + H2NCH-CONH-CH-COR R O2N NHCHCONH-CHCO- +HF NO2 R R

Phn ng ny c dng xc nh trt t sp xp cc n v aminoixit trong phn t peptit (Phng php Sanger). c, Phn ng mu biure 17Trng THPT chuyn Tn Ph- nh Qun


Phn ng mu biure c trng cho lin kt peptit, tt c c peptit c t hai lin kt peptit tr ln u phn ng vi dung dch CuSO4 long trong mi trng kim cho dung dch hp cht phc c mu tm hoc tm . Phn ng biure c dng phntch nh tnh (nhn bit) v phn tch nh lng peptit v prrotein. IV - Tng hp peptit: Khc vi nhiu loi hp cht hu c khc, cc phn ng tng hp (iu ch) peptit rt phc tp. Khng th tng hp c peptit mong mun nh phn ng trng ngng cc phn t aminoaxit khc nhau, v s to ra hn hp cc peptit. V d trng hp n gin nht l ngng t hai phn t aminoaxit khc nhau s to ra 4 ipeptit: Gly-GlyGlixin + Alanin -H2O Ala-Ala Gly-Ala Ala-Gly

Do vy tng hp mt peptit c trt t xc nh cc n v aminoaxit trong phn t cn phi bo v nhm amino hay nhm cacboxyl no khi khng cn chngs tham gia phn ng to ra lin kt peptit. Nhm bo v cn tho mn mt s tiu chun sau: - D gn vo phn t aminoaxit. - Bo v c nhm chc trong iu kin hnh thnh cc lin kt peptit. - D loi ra m khng nh hng n s tn ti ca cc lin kt peptit. 1. Bo v nhm amino: Nhm amino thng c bo v bi nhm benzyloxicacbonyl (C6H5 - CH2O - C -, cn gi l O cacbobenzonxi v c k hiu l Cbz) bng cch cho aminoaxit phn ng vi benzyl clofomiat (C6H5-CH2-O-CO-Cl, cacbonbenzoxi clorua) trong dung dch. V d:

+H3O

C6H5CH2OCOCl+ H3NCH2COO

-

dd NaOH 5oC - 30 pht

C6H5CH2OCONHCH2COO

+

C6H5CH2OCONHCH2COOH

Benzyloxicacbonylglyxyl Sau khi tng hp c peptit nhm bo v s c loi ra khi phn t peptit nh phn ng hiro phn: H2/Pd C6H5CH2-OCONHCHCO NHCHCO-... R R1C6H5CH3

+ HOCONHCHCOR

NHCHCO-... R1

CO2 +

H2NCHCO R

NHCHCO-... R1

2. Bo v nhm cacboxyl: Nhm cacbonxyl thng c bo v bng cch chuyn thnh metyl hay etyl hoc benzyl este. Nhm este d thu phn hn nhm peptit nn c loi ra khi phn t peptit bng cch thu phn bi dung dch kim:



C6H5CH3

+ HOCONHCHCO

+ CH3OH ...- C-NHCH(R1)-COOH O Ring nhm benzyloxi (C6H5CH2O-) cn c loi nh phn ng hiro phn: H2/Pd ...- C-NH(R)CH-COOH + C6H5CH3 ...- C-NHCH-CO(R)OCH2C6H5 O O

...- C-NHCH(R)-COOCH3 O

NHCHCO-... R R1 H3O+ OH/H2O

CO2 +

H2NCHCO R

NHCHCO-... R1

3. Ngng t cc aminoaxit c bo v Thc hin phn ng ngng t cc aminoaxit c nhm chc c bo v s thu c peptit mong mun. V d tng hp i peptitthreonylalanin:C6H5CH2OCONHCH-COOH + H2NCHCOOCH2C6H5 CH3CHOH Thre onin b v -NH2 o DDC -H2O H2/Pd/C CH3COOH CH3 Ala b v-COOH nin o HNCHCOOCH2C6H5 DDC -H2O

C6H5OCONHCH-CO

CH3CHOH CH3 Cbz-Thr-Ala- -CH2C6H5 _ + H3NCH-CO HNCHCOO + 2 C6H5CH3 + CO2 CH3CHOH CH3

V XC NH CU TRC xc nh cu trc ca peptit thng thc hin cc bc c bn sau: 1. Xc nh thnh phn cc aminoaxit trong phn t peptit: Thu phn hon ton peptit thnh hn hp cc aminoaxit (thng thu phn bng dung dch HCl 6N 1100C trong khong 24-72 gi). Sau khi lm sch dung dch thu phn, tch ring tng aminoaxit nh phng php sc k. nhn bit tng aminoaxit cn tin hnh sc k thm mt dung dch chun cha hn hp cc aminoaxit bit v c nng xc nh. So snh cc sc k ca dung dch chun s bit c thnh phn v t l tng aminoaxit trong phn t peptit. 2. Xc nh trnh t sp xp cc n v aminoaxit trong phn t peptit: 2.1. Xc nh aminoaxit u N - Phng php Sanger Cho peptit phn ng vi 2,4-initro-flobenzen thu c dn xut 2,4-initrophenyl ca peptit. Thu phn dn xut ny trong mi trng axit thu c hn hp cc aminoaxit v 2,4initrophenyl ca aminoaxit u N, dn xut DNP ca aminoaxit c th nhn bit c bng cc phng php sc k, t suy ra n v aminoaxit u N:



NO2 O2N F + H2NCH-CONH-CH-COR R 2,4-dinitroflobenzen NO2 HCl, to O2N O2N NHCHCONH-CHCONO2 + R R

NHCHCOOH R

H3N+ CH-COO R

N-(2,4-initrophenyl) aminoaxit - Phng php Edman Cho peptit tc dng vi phenylosothioxionat C6H5N=C=S, nhm NH2 ca n v aminoaxit u N phn ng to ra dn xut penylisothicacbamonyl peptit (dn xut phenyl thioure ca peptit), sau cho dn xut thu c tc dng vi HCl trong mitrometan s xy ra s phn ct lin kt peptit gc aminoaxit u N, to thnh peptit ngn hn v phenylthiohiantoin: Ph Ph Ph N=C=S N phenyl iso thioxyanat C=S C=S + O=C NH2 NH HCl R CH NH R CH R CH H2O phenyl thiohydantoin C=O C=O + NH NH NH2 R' CH R' CH R' CH C=O C=O C=O NH NH NH R'' CH R'' CH R'' CH C=O C=O C=O peptit phenylthiocacbamoylpeptit peptit ngn hn Sn phm phenylthiohiantoin c nhn bit nh phng php sc k, trn c s so snh vi cht chun bit c th suy ra aminoaxit u N, peptit ngn hn c tinh ch v li tip tc thc hin phng php Edman nhn ra n v aminoaxit u N ca n... 2.2. Xc nh aminoaxit u C Thu phn peptit nh enzim cacboxipeptiaza -NH-CHR3-CO-NH-CHR2-CO-CHR1-COO- cacboxypep tidz -NH-CHR3-CO-NH-CHR2-COO+-NH3+ CHR1-COOAminoaxit xut hin u tin trong dung dch chnh l aminoaxit u C. Hn ch ca phng php ny l enzim cacboxipeptidata khng tch c cc aminoaxit ui C l prolin hoc hiroxiprolin ra khi mch peptit. 2.3. Thu phn tng phn mch peptit Thu phn peptit nh cc enzim proteaza (tripsin, chimotripsin, pepsin...) thu c hn hp cc peptit c mch ngn hn; cc peptit ny c tch ring nh phng php sc k, tinh ch 20

Trng THPT chuyn Tn Ph- nh Qun


sch r xc nh trnh t sp xp cc n v aminoaxit trong phn t ca chng theo cc phng php nu trn. phn ct peptit thnh cc peptit c mch ngn hn cn dng cc tc nhn xian bromua BrCN. Tc nhn ny ch phn ct mch peptit sau gc methiomin:H N CH CH2 O C N H R CH C OH

BrCN

N CH

CO O H2C CH2 +

R CH H2N CO + CH3SCN

CH2SCH3

homoserin lacton i vi mt mch peptit, nu dng cc xc tc phn ct mch khc nhau s thu c nhng phn on khc nhau. Chng hn phn ct on mch sau: Phn ct bng trypsin Ala Leu Gly Met Lys Trp Phe Arg Ala Ala Ser Met Ala Phe Lys Phn ct bng BrCN



MT S BI TP V HP CHT CA NITCu 1: ( thi HSG quc gia nm 2000-2001) Xut pht t Brombenzen cha 14C v tr 1 v cc ha cht v c cn thit khng cha 14C, hy iu ch cc hp cht thm cha 14C v tr 3: a) anilin b) Iotbenzen c) Axit benzoic Cu 2: So snh tnh baz ca cc hp cht sau y: R3N, R2NH, RNH2 Gii thch v sao c s sp xp ? Cu 3: (Chn i HSG Tnh 2006- 2007) Mt pentapeptit (A) khi thu phn hon ton cho 2 mol Gly, 1 mol Ala, 1 mol Val v 1mol Phe. Trong s thu phn tng phn (A) thy c Ala-Gly, Gly-Ala. A tc dng vi HNO2 khng thy gii phng N2. Xc nh cng thc cu to ca A. Cu 4: Mui C6H5N2+Cl- (phenyliazoni clorua) c sinh ra khi cho C6H5-NH2 (anilin) tc o dng vi NaNO2 trong dung dch HCl nhit thp (0-5 C). iu ch c 14,05 gam + C6H5N2 Cl (vi hiu sut 100%), lng C6H5-NH2 v NaNO2 cn dng va l A. 0,1 mol v 0,4 mol. B.0,1 mol v 0,2 mol. C.0,1 mol v 0,1 mol. D.0,1 mol v 0,3 mol. Cu 5: Cho 8,9 gam mt hp cht hu c X c cng thc phn t C3H7O2N phn ng vi 100 ml dung dch NaOH 1,5M. Sau khi phn ng xy ra hon ton, c cn dung dch thu c 11,7 gam cht rn. Cng thc cu to thu gn ca X l A. HCOOH3NCH=CH2. B. H2NCH2CH2COOH. C. CH2=CHCOONH4. D. H2NCH2COOCH3. ( thi H 2008) Cu 6: C cc dung dch ring bit sau y: C6HH5NH3Cl(phenylamoniclorua, H2N-CH2-CH2-CH(NH2)-COOH, ClH3N-CH2-COOH, HOOC-CH2-CH2-CH(NH2)-COOH, H2N-CH2-COONa. S lng cc dung dch c pH 6). Cu 14: ( thi HSG quc gia - 2003) 1.Hp cht A (C5H11O2N) l mt cht lng quang hot. Kh A bng H2 c xc tc Ni s c B (C5H13N) quang hot. Cho B tc dng vi axit HNO2 thu c hn hp gm ancol C quang hot v ancol tert-amylic (2- metyl-2-butanol). Xc nh cng thc cu to ca A. Dng cng thc cu to, vit phng trnh cc phn ng to thnh B, C v ancol tert-amylic t A. 2.Hp cht A (C5H9OBr) khi tc dng vi dung dch it trong kim to kt ta mu vng. A tc dng vi dung dch NaOH to ra 2 xeton B v C cng c cng thc phn t C5H8O. B, C u khng lm mt mu dung dch kalipemanganat lnh, ch c B to kt ta mu vng vi dung dch it trong kim. Cho B tc dng vi CH3MgBr ri vi H2O th c D (C6H12O). D tc dng vi HBr to ra hai ng phn cu to E v F c cng thc phn t C6H11Br trong ch c E lm mt mu dung dch kalipemanganat lnh. Dng cng thc cu to, vit s phn ng t A to thnh B, C, D, E, F. Vit tn A v D theo danh php IUPAC. Cu 15: ( thi HSG quc gia - 2005) L-Prolin hay axit (S)-piroliin-2-cacboxylic c pK1 = 1,99 v pK2 = 10,60. Piroliin (C4H9N) l amin vng no nm cnh. 1. Vit cng thc Fis v cng thc phi cnh ca L-prolin. Tnh pHI ca hp cht ny. 2. Tnh gn ng t l dng proton ho H2A+ v dng trung ho HA ca prolin pH = 2,50. 3. Tnh gn ng t l dng eproton ho A v dng trung ho HA ca prolin pH = 9,70. 4. T metylamin v cc ho cht cn thit khc (benzen, etyl acrilat, natri etylat v cc cht v c), hy vit s iu ch N-metyl-4-phenylpiperiin. Bi 16: ( thi HSG quc gia, Vit Nam - 2007) 1. Thy phn hon ton mt hexapeptit M thu c Ala, Arg, Gly, Ile, Phe v Tyr. Cc peptit E (cha Phe, Arg) v G (cha Arg, Ile, Phe) c to thnh trong s cc sn phm thy phn khng hon ton M. Dng 2,4-dinitroflobenzen xc nh c amino axit Ala. Thy phn M nh tripsin thu c tripeptit A (cha Ala, Arg, Tyr) v mt cht B. a. Xc nh th t lin kt ca cc amino axit trong M. b. Amino axit no c pHI ln nht v amino axit no c pHI nh nht? Bit cu to chung ca cc amino axit l H2N-CHR-COOH AA: Ala Arg Gly Ile Phe Tyr 24Trng THPT chuyn Tn Ph- nh Qun

N H

COOH


R : CH3 (CH2)3NHC(=NH)NH2 H CH(CH3)C2H5 CH2C6H5 p-HOC6H4CH2 2. Isoleuxin c iu ch theo dy cc phn ng sau (A, B, C, D l k hiu cc cht cn tm):CH3CH2(C 2 H 5OOC) 2 CH 2 A CH CH3 . KOH 1

C2H5ONa 2. HCl Hy cho bit cng thc ca cc cht A, B, C, D v Isoleuxin. Cu 17: ( chon i tuyn QT 2006) Ala, Val, Leu l ch vit tt tn cc aminoaxit thin nhin, cng thc ln lt l CH3CH(NH2)COOH, (CH3)2CHCH(NH2)COOH, (CH3)2CHCH2CH(NH2)COOH. 1. Vit cc phng trnh phn ng tng hp tripeptit Leu-Ala-Val t cc cht: Ala, Val, Leu, photpho pentaclorua, BOC-Cl (tert-butyloxicacbonyl clorua), ancol benzylic, DCC (ixiclohexylcacboiimit), axit trifloaxetic, axit axetic, hiro, palai v cacbon. 2. C bao nhiu tripeptit c to thnh m mi tripeptit c 3 aminoaxit trn, nu khng s dng nhm bo v. 3. Biu din cng thc phi cnh ca tripeptit Leu-Ala-Val. 4. Ghi gi tr pKa vo nhm tng ng v tnh pHI ca tripeptit ny, bit rng pKa1 = = 3,42; pKa2 = 7,94.Br

B B r2

C

t

0

D NH Isoleuxin 3



MT S BI TP C LI GIIV d 1: Di tc dng ca in trng, aminoaxit di chuyn v pha in cc no khi pH < pI, (b) pH > pI v pH = pI ? Gii thch. Bi gii: pH < pI: cation A chim u th, nn di chuyn v pha catot, (b) pH > pI : anion C chim u th nn di chuyn v pha anot v (c) khi pH = pI in tch cn bng nn amino axit khng chuyn dch. V d 2: Vit cn bng in ly ca lysin (mt baz) v tnh im ng in ca n. Xem gi tri pKa trong bng Bi gii: COOCOOH CHNH3 CHNH3 (CH2)3 (CH2)3 CH2NH3 CH2NH3 (+2) COO COO

OH OH H H(+1)

CHNH2 (CH2)3 CH2NH3

OH H

CHNH2 (CH2)3 CH2NH2

(0)

(-1)

in tch tng cng ca mi dng c ghi trong ngoc n trn, dng c in tch bng khng tn ti gia hai dng c pKa tng ng l 8,95 v 10,53. Nh vy pI = (8,95+10,53)/2 = 9,74. V d 3: Vit cn bng in ly ca axit aspatic v tnh im ng in ca n. Bi gii: COO COOHCHNH2 CHNH3 CH2 CH2 COO COOH COO CHNH3 COO

OH HCH2 COOH

OH H

CHNH3 CH2 COO

OH H

(+1)

(0)

(-1)

(-2)

Dng c in tch bng khng tn ti gia hai dng c pKa tng ng l 1,88 v 3,65. Nh vy pI = (1,88 + 3,65)/2 = 2,77. V d 4: Khi thy phn hon ton 1 mol tripeptit X thu c 2 mol axit glutamic [HOOC(CH2)2CH(NH2)COOH], 1 mol alanin [CH3CH(NH2)COOH] v 1 mol NH3. Cht X khng phn ng vi 2,4-dinitroflobenzen v X ch c mt nhm cacboxyl t do. Thy phn X nh enzim cacboxipeptidaza thu c alanin v mt dipeptit Y. Vit cng thc cu to ca X, Y v gi tn chng. Bi gii: Xc nh cu to X v Y : -Thy phn X nh enzim cacboxipeptidaza thu c alanin v mt dipeptit Y aminoaxit Cu mch l Ala v nh vy tripeptit X c cu to theo trt t : Glu-Glu-Ala. -X khng phn ng vi 2,4-dinitroflobenzen v X ch c mt nhm cacboxyl t do nhm -NH2 ca aminoaxit N-u mch to lactam vi nhm cacboxyl ca Glu th nht. 26Trng THPT chuyn Tn Ph- nh Qun


-Khi thy phn hon ton 1 mol tripeptit X thu c 1 mol NH3 nhm cacboxyl ca Glu th hai tn ti dng amit -CONH2. Vy X v Y l :NH CH CO NH CH CO NH CH COOH (CH2)2CONH 2 CH2 CH2 CH3

X:

O

C

Glutamolactam ylglutaminylalanin NH CH CO NH

Y:

O

C CH2 CH2

CH COOH (CH2)2CONH 2

Glutamolactam ylglutamin V d 5: Xc nh cng thc cu to v tn ca A(C 3H7O2N). Bit rng A c tnh cht lng tnh, phn ng vi axit nitr gii phng nit; vi ancol etylic c axit lm xc tc to thnh hp cht c cng thc C5H11O2N. Khi un nng A chuyn thnh hp cht vng c cng thc C 6H10N2O2. Hy vit y cc phng trnh phn ng xy ra v ghi iu kin (nu c). A c ng phn loi g ? Bi gii: a) Cng thc cu to ca A : A phn ng vi axit nitr gii phng nit A cha nhm -NH2 A phn ng vi ancol etylic to C5H11O2N A cha nhm -COOH un nng A to hp cht vng C6H10N2O2 A l -aminoaxit Cng thc cu to ca A : CH3CH(NH2)COOH (alanin) b) Phng trnh phn ng :15 7 1 O2 3CO2 + H2O + N2 4 2 2 CH3 CH COOH + HONO CH3 CH COOH + N2 + H 2O NH2 OH HCl CH3 CH COOH + C2H5OH CH3 CH COOC 2H5 + H 2O C3H7O2N +

CH3

NH2 CH COOH + NH 3 NH3Cl to CH3 HN O O

CH3

NH3Cl CH COOC 2H5 + NH 4Cl NH2

2 CH3 CH COOH NH2

NH

+ H 2O

CH3

(c) A c ng phn quang hc do phn t c nguyn t cacbon bt i :COOH H C NH2 CH3 COOH H2 N C H CH3



V d 6: Xut pht t brombenzen cha 14 C v tr 1 v cc ho cht v c cn thit khng cha 14 C, hy iu ch cc hp cht thm cha 14 C v tr 3 : a) Anilin ; b) Iotbenzen ; c) Axit benzoic. Bi gii: a, Br MgBr14

C

14

+MgBr14

Mg

ete khan

C

(1)COOMgBr

C

+

CO2

(2)

COOMgBr

COOH

+

+ H3O

(3)

COOH14

COOH14

C

+COOH14

HNO3

H2SO4

C

+NO2COONa14

HOH

(4)

C

C NO2

2NO2 COONa14

+

Na2CO3

2

+ HOH + CO2

(5)

C

14

+NO214

NaOH r n

CaO

C

+NO214

Na2CO3

(6)

C

C

+NO214

3 Fe +

7 HCl14

+ 3 FeCl3 + 2 HOH NH3Cl + NaClNH2

(7)

C

C

+ NaOHNH3Cl

+ HOH

(8)



b,14

C + NaNO2 NH214

14

C N N +

+ 2 HCl

Cl +

NaCl + 2HOH (9)

C N N +

14

Cl +

C I + N2 + KCl (10)

KI

c,14

C N N + Cl + CuCN

14

C N2 C14

+

CuCl (11)

N + COOH + NH4

14

C + C N 2HOH + H+

C

2

(12)

V d 7:( thi HSG quc gia 1997) Thu phn hon ton 1mol polipeptit X cho ta: 2mol CH3 - CH(NH2) - COOH (Alanin hay vit tt l Ala). 1mol (HOOC - CH2 - CH2 - CH(NH2) - COOH (axit gluconic hay Glu). 1mol H2N-(CH2)4-CH(NH2)-COOH (Lizin hay Lis) 1mol (Histidin hay His) N CH2 CH COOH NH2 N H Nu cho X tc dng vi 2,4 (NO 2)2 C6H3F (k hiu ArF) ri mi thy phn th tm c Ala, Glu, Lys v hp cht N CH2 CH COOH N NH Ar H Mt khc nu thu phn X nh enzim cacboxipetidaza th thu c Lys v mt tetrapeptit. Ngoi ra khi thu phn khng hon ton X cho ta cc ipeptit Ala - Glu, Ala-Ala v His- Ala. 1. Xc nh cng thc cu to v tn ca poliptit X. 2. Sp xp cc aminoaxit trn theo th t tng dn pHI(pHI c gi l im ng in, ti pH d aminoaxit tn ti dng ion tng cc trung ho v in tch v khng di chuyn v mt din cc no c). Bit gi tr pHI l 3,22 ; 6,0; 7,59; 9,74. 3. Vit cng thc cu to dng ch yu ca mi aminoaxit trn cc pH bng 1v 13.



4. Di tc dng ca enzim thch hp aminoaxit c th b decacboxyl ho (tch nhm cacboxyl). Vit cng thc cu to ca cc sn phm ecacboxyl ho Ala v His. So snh tnh baz ca cc nguyn t nit trong phn t gia hai sn phm . Gii thch. Bi gii: 1. T s mol v cng thc cu to ca cc aminoaxit suy ra X l mt pentapeptit. T kt ta thu phn sn phm phn ng gia X v ArF suy ra u N (u cha nhm -NH2 t do) ca X l His. T sn phm thu phn X nh enzim cacboxipeptitdaza suy ra u C (u cha nhm -COOH t do) ca X l Lys. Khi thu phn khng hon ton X cho cc ipeptit His-Ala, Ala-Ala, Ala-Glu. Trt t sp xp cc aminoaxit trong mch: His - Ala - Ala - Glu Lys. Cng thc cu to ca X:

H2N - CH - C - NH - CH - C - NH - CH - C - NH - CH - C - NH - CH - COOH CH3 O CH3 O O O (CH2 )2 (CH2 )2 N CH2 N HCOOH NH2

(Th sinh c th vit cng thc trong nhm - CO NH - gia Glu v Lys c to ra bi nhm COOH v tr ca Glu vi nhm NH2 v tr ca Lys.1.

Th t tng dn pHI: Glu pHI 3.22 < Ala 6.00 < His 7.59 < Lys 9.74

Gii thch: tnh axit ca aminoaxit cng ln th gi tr pHI cng nh, tnh baz cng ln th pHI cng ln. - Glu c pHI nh nht (3.22) v s nhm COOH nhiu hn s nhm NH2. Mun tn ti dng HOOC - (CH2)2 CH - COO phi thm H+ (a v pH thp) nhm -COOH th hai khng phn li. NH2 - Lys c pHI ln nht (9.74) v s nhm -NH2 nhiu hn s nhm -COOH. - Ala c pHI = 6.00 v c mt nhm -COOH v mt nhm -NH2. - His c pHI trung gian gia Ala v Lys, v tuy c s nhm -COOH v - NH 2 bng nhau nhng d vng cha N cng l trung tm baz (tuy yu hn -NH2). 30Trng THPT chuyn Tn Ph- nh Qun


3. Ala :

pH = 1

pH = 13

CH3 - CH - COOH +NH3

CH3 - CH - COONH2

Glu : HOOC - (CH2)2 - CH - COOH

-OOC - (CH2)2 - CH - COONH2

+NH3+ His : H N

CH2-CH-COOH N H +NH3

N N H

CH2-CH-COONH2

+ Lys:

H3N - (CH2)4 - CH - COOH +NH3 H2N - (CH2)4 - CH - COONH2

4.

CH3 - CH - COOH NH2

enzim

-CO2

CH3 CH2 NH2 (c)

N N H

CH2-CH-COOH NH2

Nenzim

CH2-CH2-NH2 N H

-CO2

(d)

- Tnh baz gim dn: N(a) > N(b) > N(c) > N(d). Gii thch: Tnh baz nguyn t N tng khi mt electron trn n tng. Mt electron N(a) > N(b) v N(a) lin kt vi gc C2H5 y e, trong khi N(b) nh hng bi gc d vng ht e. Mt e N(c) < N(b) v N(c) trng thi lai ho sp2 (c m in ln hn nguyn t N (b) lai ho sp3). V N(c) li lin kt vi nhng nguyn t C lai ho sp 2 (kh nng ht e ca C lai ho sp2 31Trng THPT chuyn Tn Ph- nh Qun


mnh hn C lai ho sp3). N(d) khng c tnh baz v khng cn cp electron t do (do tham gia to h lin kt trong vng thm). V d 8: ( thi HSG quc gia 2008) 1. a, HSCH2CH(NH2)COOH (xistein) c cc pKa: 1,96; 8,18; 10,28. Cc cht tng ng vi n l HOCH2CH(NH2)COOH (serin), HseCH2CH(NH2)COOH (selenoxistein), C3H7NO5S (axit xisteic). Hy xc nh cu hnh R/S i vi serin v axit xisteic. B, Hy qui kt cc gi tr pKa cho tng nhm chc trong phn t xistein. Vit cng thc ca xistein khi Ph = 1,5 v 5,5. 2. Sp xp 4 amino axit trn theo th t tng dn gi tr PhI v gii thch s sp xp . 3. Thy phn hon ton mt nonapeptit X thu c Arg, Ala, Met, Ser, Lys, Phe2, Val, v Ile. S dng phn ng ca X vi 2,4-initroflobenzen xc nh c Ala. Thu phn X vi trypsin thu c pentapeptit (Lys, Met, Ser, Ala, Phe), ipeptit (Arg, Ile) v ipeptit (Val, Phe). Thu phn X vi BrCN dn n s to thnh mt tripeptit (Ser, Ala, Met) v mt hexapeptit. Thu phn vi cacboxypeptiaza c X v hexapeptit u cho Val. Xc nh th t cc amino axit trong X. Bi gii: 1. a.Xc nh cu hnhCOO H 3N H CH2OH L-Serin (cu h S) nh H 3N COOH H CH2SO3 Axit L-xisteic (cu h R) nh

b. Gi tr Ph v cng thc ca xistein pKa (xistein): 1,96 (COOH) ; 8,18 (SH) ; 10,28 (NH2) PhI (xistein) = (1,96 + 8,18) / 2 = 5,07 + Ph = 1,5 : HS CH2 CH (NH3) COOH + Ph = 5,5 : HS CH2 CH (NH3) COO2.Trt t PhI Trnh t tng dn PhI : Axit xisteic < selenoxistein < xistein < serin 3.Xc nh cng thc cng thc ca X Theo bi xc nh c u N l Ala; u C l Val. Thy phn vi trypsin thu c: Ala-(Met, Ser, Phe)-Lys Ile-Arg v Phe-Val Da vo kt qu thy phn vi BrCN, suy ra: Ala-Ser-Met-Phe-Lys Vy X l: Ala-Ser-Met-Phe-Lys-Ile-Arg-Phe-Val V d 9: Sp xp s tng dn tnh baz (c gii thch) ca cc cht trong tng dy sau: Sp xp s tng dn tnh baz (c gii thch) ca cc cht trong tng dy sau: 1. CH3-CH(NH2)-COOH , CH2=CH-CH2-NH2 , CH3-CH2-CH2-NH2 , CH C-CH2-NH2. 2.NH

CH3 ,

CH2

NH2 ,

CH2 NH2 , O2N

NH2



Bi gii: Tnh baz tng theo th t: 1.CH3-CH(NH3)+-COO- < CH C-CH2-NH2 < CH2=CH-CH2-NH2 < CH3-CH2-CH2-NH2 Tn ti dng ion lng cc 2.O2N NH2 < CH2-NH2 < CH2-NH2 < NH -CH3

m in CSP

>

CSP2

>

CSP3

Nhm p-O2N-C6H4ht e mnh do c nhm -NO2 (-I -C) lm gim nhiu mt e trn nhm -NH2

Nhm C6H4-CH2ht e yu

Nhm C6H11-CH2y e, lm tng mt e trn nhm NH2

- Nhm C6H11v -CH3 y e, - Amin bc II


Chuyen de Huu Co HSG THPT

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