Last Name First Name 10 No. Question 1. (12 points) Draw the structures of the following compounds. Indicate which member of the following pairs of compounds reacts faster in the SN1 reaction and which reacts faster in the SN2 reaction. Concisely explain your reasoning. A. 1-chloropentane B. cyclopentyl chloride A or B reacts faster in SN1 reaction B A or B reacts faster in SN2reaction A. tert-butyl iodide B. tert-butyl chloride A or B reacts faster in SN1 reaction A or B reacts faster in SN2reaction /II/A Structure of A Structure of B ce Rationale B form.5 W\.Oye CdJY b 0 C-d.- -t j 0 h. Rationale ~ ,$ t..SS h"Y\Je.~€.-cl ~k~ ~k Structure of A Structure of B Rationale I \h is cyrou p. Page 2 of 10
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Last Name First Name 10 No.
Question 1. (12 points) Draw the structures of the following compounds. Indicate which
member of the following pairs of compounds reacts faster in the SN1 reaction and which reacts
faster in the SN2 reaction. Concisely explain your reasoning.
A. 1-chloropentane
B. cyclopentyl chloride
A or B reacts faster in
SN1 reaction
B
A or B reacts faster in
SN2reaction
A. tert-butyl iodide
B. tert-butyl chloride
A or B reacts faster in
SN1 reaction
A or B reacts faster in
SN2reaction
/II/A
Structure of A Structure of B
ce
Rationale
B form.5 W\.Oye
CdJY b 0 C-d.--t j 0 h.
Rationale
~ ,$ t..SS h"Y\Je.~€.-cl
~k~ ~k
Structure of A Structure of B
Rationale
I \h is
cyrou p.
Page 2 of 10
Last Name First Name IDNo.
Question 2. (20 points) For each of the following reactions, give the substitution products and
the corresponding transition state of the SN2 reactions or intermediates for the SN1 reactions. If
the products can exist as stereoisomers, show what stereoisomers are obtained. Also indicate
the absolute configuration (R or S) of each chiral center in the products. Hint: drawing out the
structure of reactants might be helpful.
Reactant
trans-1-chloro-2-methylcyclohexane
Intermediate(s) or transition-state(s)
Reagent(s)
High concentration of CH30Na
H
Products
H
Page 3 of 10
Last Name First Name IDNo.
Question 2, continued.
Reactant
trans-1-chloro-2-methylcyclohexane
Intermediate(s) or transition-state(s)
Products
ocU~
C.H~
Reagent( s)
CH30H
~
i
cu:,h"ral .
COmpOLU\J. .
Page4of10
ocK~
CH~
~-., --.----
Last Name First Name IDNo.
Question 3. (18 points) The structure of amino acid threonine is shown below. The amino acidcarbon(C2)bearsan S-configuration. .
C2~~H2 C3
OH C4
Draw all possible stereoisomers for theorine (with C2 in S-configuration) and clearly show
the absolute configuration (R or S) at each chiral center using perspective formulas with
solid and hatched wedges.
a.
b. How are each of these stereoisomers (in part b) related to the others? Are they
enantiomers or diastereomers? d'\ a s1£ ye.VW\.Q.. r 5c. For the two isomers in part at state whether the following properties are the same or not.
d. Draw a representative Newman projection for each stereoisomer by looking"down from C2
to C3, showing the staggered conformations.
1V'J..f2.
H ... ~ / Et
H" Y "COJlk
'H
H
/l/H2,
Jk.
CO~H
Et
Page 5 of 10
.
Properties Same Different
Meltingpoint V13C NMR spectra VMolecular weight V
Taste VSpecificrotation V
Last Name First Name 10 No.
Question 4. (25 points) Using ethyne (HC5CH), and other compounds that contain one or no
carbon atom-if necessary, as the starting materials, how can the following compounds be
prepared? For each step of your proposed synthesis, the product that will be used as the starting
material for the next step should be the major reaction product for that step (Le., over 50% yield).
o
~HA.
Page 6 of 10
Last Name First Name
Question 4, continued.
B.~Br
PA-CH,-~ C R.- C Ho «H 5r
pe YO){, de,
10No.
He - C - Cf13N~ 0)' Li I AIJ.1:.{ e~1-.)
OY
Lih~ ~st
H c== C H A/...A/U...He ==c9(1-1>0CI-I'-CH,J'JJ-1
~ C -== c H - e'l - C H- c H (Nu..- 01' li, NJ./Jli}'JHC= C - CH - cH - CH2. M2. 2. 3 Qt: 1.. -z. 3
.1' B1
.. I. Liholk "',.,+.AOu-stn r p0'roX IO\L V\A/"'d
H;c- (HL- 0(- C 1-17.. - CI-tBy
Page 7 of 10
i
Last Name First Name 10No.
Question 5. (10 points) Give the absolute configurations (R or S) of the final products obtained
from the following reactions and answer the questions listed in the table.
1. Na, NH3 (liq)~
2.D2.Pd/C
Products of the first step
Products of the second step and the absolute configurations
D
HEt
For the final products, what are the relationships between the isomers?
~io m..Q/YS
Is each stereoisomer optical active?
Is the reaction mixture optical active and why?
AID it ISJ m ixkeHow many 13C-NMR signal you expect for each isomer and the mixtures of final product?
3 ::'i~ds for. eO--Gh iso~
3 Si~S for -tk mixke of prodJM:t
Page 8 of 10
Last Name First Name 10No.
Bonus question (6 points) S-Adenosylmethionine (AdoMet), depicted below, is sold under the
name SAM-e as a nutrition supplement for the treatment of arthritis and depression. As
mentioned in the textbook, biological systems use adenosylmethionine as a methylation agent.
However, adenosylmethionine spontaneously decomposes in aqueous solutions. One of the
major decomposition products is methylthioadenosine (MTA), and the other major product has a
formula of C4H7N02. The decomposition rate is markedly reduced at reduced pH (about 3).
Please propose a mechanism for this decomposition reaction.
NHz
yH3 ~N0N
s~-lN)OH OH
MTA
+
:OU2.
Page 9 of 10
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