Oct 24, 2014
What is carbon compound ???
- Compound that contains carbon , C combined with other elements .
Carbon compounds
Organic compounds
Inorganic compounds
-a carbon compound -normally found in found in , produced by, mineral and water or derived from living resources organism -eg. CO32-, HCO3Eg. Protein , carbohydrate , cyanide ,CN- , fat , vitamins ,petroleum, carbide,C4-, natural gas , antibiotic , CO2 , CO natural rubber , plastic , detergent , pesticides
Most organic compounds contain the elements C and H. Hence complete combustion of organic compounds produces CO2 + H2O Organic CompoundsComplete combustion
CO2 +
H2O
ACTIVITY 2.1 LATIHAN 2UCombustion of organic compounds and their product .
WHY IS CARBON UNIQUE ??1. 2. 3. Forms four covalent bonds Bonds covalently to: H, O, N, P, S, and all other nonmetals (except noble gases) Carbon atoms join to form: Chains and Rings
CH3CH2CH2CH3 CH3CH2CH2CH3
H2 H2 C C H2C CH2 H2C CH2 H2C CH2 H C CH2 2
WHY IS CARBON UNIQUE ??
4. Carbon can form multiple bonds to itself, oxygen, and nitrogen. Example:
C-C (single bond)C=C (double bond) C=C (triple bond)
CLASSIFICATION OF ORGANIC COMPOUNDS Organic compounds
Hydrocarbons
Non-hydrocarbons Carboxylic esters Acids
- An organic compound that contains only Alcohols carbon ,C and hydrogen ,H
Aromatic
Aliphatic
Alkanes
Alkenes
Alkynes
HYDROCARBON-organic compounds that contain only carbon, C and hydrogen ,H
SATURATED HYDROCARBON-Hydrocarbons that contain only single covalent bonds between the carbon atoms
UNSATURATED HYDROCARBON-Hydrocarbons that contain double or triple bonds between the carbon atoms
Eg. alkane
Eg. Alkene, Alkyne
The main source of hydrocarbons is natural gas and petroleum
HOMOLOGOUS SERIES
-is a group of organic compounds in which each member differs from the next one in the series by a fixed unit of structure .-
CH2 unit
-Eg. Alkane , alkene , alkyne , alcohols , carboxylic acids , esters.
CHARACTERISTIC OF HOMOLOGOUS SERIES1.Members of the series can be represented by a general formula. 2. Successive members differ from each other by CH2 3. Physical properties change regularly with increasing number of carbon atoms per molecule .
4. Members have similar chemical properties because they have the same functional group. 5. Members can be prepared by similar methods
What is a functional group ??-An atom or group of atoms that is responsible for the similar chemical properties of a homologous series .
Eg. Double bond (C=C) , triple bond (C=C) hydroxyl (-OH) ,carboxyl (COOH) , ester (COOR)
EXAMPLE OF HOMOLOGOUS SERIESHOMOLOGOUS SERIES GENERAL FORMULA
FUNCTIONAL GROUP
ALKANES CnH2n+2 ,n =1,2,.. ALKENES ALKYNES
-C=C-C=C-OH
CnH2n , n =2,3,..CnH2n-2 , n =2,3,..
ALCOHOLS CnH2n+1OH , n=1,2,..
CARBOXYLIC C H n 2n+1COOH ,n=0,1,.. -COOH ACIDS CnH2n+1COOCmH2m+1 , ESTERS -COOR n=0,1,.. , m=1,2,
ALKANES-General formula :
CnH2n+2 ,n =1,2,..
-saturated hydrocarbon-Naming use IUPAC nomenclature - the name of a straightchain alkanes consist of two components : root & ending(ane) -root :indicates how many atoms in the longest continuous chain -ending ane : indicates the compound is a member of alkane family
NAME OF ALKANES (C1-C10)Number of C atoms
12
Root name methethprop-
IUPAC name
methaneethane
3 45
propane butanepentane
butpenthex-
67
hexane heptane octane nonane decane
8 910
heptoctnondec-
No. of C atoms
Nomenclature / Molecular formula
Structural FormulaH H C H H
1 C
Methane
CH4
2 C
Ethane
C2H6
H H C H
H C H H
3 C
H
H C H
H C H H
Propane
C3H8
H
C H
No. of C atoms
Nomenclature / Molecular formula
Structural FormulaH H C H H C H H C H H
4 C
Butane
C4H10
H
C H
6 C
Hexane
C6H14
ISOMERISM OF ALKANESIsomerism the phenomenon of organic compounds existing as isomers .
Isomers - compounds with the same molecular formulae but different structural formulae
ISOMERISM
Structural isomerism
Stereoisomerism
chain
positional
enantiomer
geometric
Functional group
Isomer have different physical properties but **similar chemical propertiesSometimes isomer have different chemical properties (different functional group)
STRUCTURAL ISOMERISM IN ALKANESPlease draw as many isomer as you can for :
1. C4H10 2. C5H123. C6H14
P/s - Give answer
Steps :
IUPAC NOMENCLATURE
1.Find the longest continuous chain of carbon atoms , and use the name of this chain as the base name of the compound.
2.Identify the substituent group3.Name and give the location of each substituent group(substituent get the lowest no)
4.When two or more substituents are present ,list them in alphabetical order . Use prefix di-(two), tri-(three), tetra-(four). 5.Number and number ( ,) number and alphabet(-)
Substituent group atom or group of atoms which attached to the longest chain . Eg. : alkyl ( a substituent group that is formed by removing an H atom from an alkane)alkane structure alkyl structure
methane ethane
CH4 CH3CH3
methyl ethyl
-CH3 -CH2CH3
propane CH3CH2CH3
propyl -CH2CH2CH3
iodo Ethyl CH2CH3
I
Longest chain
H-C-C-C-C-C-C-C-C-C-HBr CH3methyl Bromo
Cl Chloro
Examples of substituent group
Example on naming the alkane HHH H
H-C-C-C-C-HHH H C H H Step 1 longest continuous chain contains 4 C atoms . - base name : butane H
HHH H
H-C-C-C-C-HHH H C H H Step 2 identify substituent group -substituent group : methyl H
HHH H
H-C-C-C-C-HHH H C H H
HStep 3 number the carbon atom in the longest chain . How??? From left- methyl on the second C atom - From right-methyl on the third C atom Name of the alkane : 2-methylbutane
Let us draw the isomers for C4H10 , C5H12 and C6H14 .
Please name all the isomers according to the IUPAC nomenclature .
Physical Properties
a) Melting and Boiling Point* Low boiling points and melting points because Van der Waals forces between molecules are weak
b) Physical State at Room TemperatureCH4 - C4H10 : gas C5H12 - C17H38 : liquid C18H38 : solid
c) Solubility* Soluble in non polar solvents (organic solvents), insoluble in water. Why???
d) Density* The density of the alkanes increases with increasing number of carbon atoms per molecule , BUT is less than water. Hence, alkanes form the upper layer in an alkane-water mixture.
e) Electrical Conductivity
Do not conduct electricity because : alkanes are covalent compounds, do not have free moving ions but are made up of molecules
a) Melting and Boiling Point
a) Melting and Boiling Point
The boiling point increases between 20 -30 C per -CH2 group.Boiling points and melting points increase as number of carbon atoms per molecule increases. Then, size of molecules increases (molecular mass increases) Forces between molecules (van der Waals forces) are stronger
More heat energy is needed to overcome the forces
CHEMICAL PROPERTIES OF ALKANES Alkanes - non-polar , saturated hydrocarbons, without any functional group. -these make alkanes nonreactive . -they do not react with acids,alkalis, oxidizing agents or reducing agents -but,under right condition,alkanes may undergo substitution or elimination reactions
REACTION 1 : COMBUSTION OF ALKANESi) Sufficient or excess O2 (complete combustion) Alkanes + O2 CO2 + H2O + heat ii) Not enough O2 (incomplete combustion) Alkanes + O2 CO + H2OOR
Alkanes + O2 C + H2O
Number of carbon atoms per molecule increase
Percentage of carbon in alkane increase
More sooty flame
Comparison the sootiness of the flame between pentane and octane
Percentage of = 5(12) carbon in pentane 5(12) +12(1) x 100 (C5H12) = 83.33% Percentage of carbon in octane (C8H18)
= 8(12) x 100 8(12) +18(1) = 84%
Because of % of carbon in octane is higher than in pentane , therefore octane burns with a more sooty flame compared to pentane
REACTION 2 : SUBSTITUTION REACTION( Halogenation ) In this reaction , each hydrogen atom in the alkane molecule is substituted by a halogen atom .General equation
RH + X2 RX + HXX=Cl ,Br
Condition : exposed to ultra violet light or heated to high temperature (200-4000C)Show the animation
Free-radical substitution reaction-involves initiation , propagation and termination steps uv i) Initiation step Cl2 2 Cl.
ii) propagation CH4 + Cl. step CH3. + Cl2 iii) termination step Cl. + Cl. CH3. + Cl. CH3. + CH3.
CH3. + HCl
CH3Cl + Cl. Cl2 CH3Cl CH3CH3
Chemical equation
CH4 + Cl2CH4 + 2 Cl2 CH4 + 3 Cl2
CH3Cl
+ HCl
CH2Cl2 + 2 HCl CHCl3 + 3 HCl
CH4 + 4 Cl2
CCl4
+ 4 HCl
What about bromine ??? Any colour changes ???
-General formula :
CnH2n ,n =2,3,..
-functional group : -C=C-unsaturated hydrocarbon -each member of alkenes contains at least one carbon-carbon double bond(-C=C)
-Naming use IUPAC nomenclature - alkenes are named by substituting the ending ane in the name of the corresponding alkane with ene-ending ene : indicates the compound is a member of alkenes family
NAME OF STRAIGHT CHAIN ALKENES (C2-C10)Number of C atoms
2
Root name ethprop-
IUPAC name
ethene/ethylene propene/propylene but-1-enepent-1-ene
3 45
butpenthex-
67 8
heptoctnondec-
hex-1-ene hept-1-ene oct-1-ene non-1-ene dec-1-ene
910
Steps :
IUPAC NOMENCLATURE
1.Find the longest continuous carbon chain containing the double bond (main chain). use the name of this chain as the base name of the compound. 2.Identify the substituent group 3.The location of the double bond is shown by a number. The numbering starts from the end of the main chain that gives a lower number to the C=C. (also state the location of substituent)
4.When two or more substituents are present ,list them in alphabetical order . Use prefix di-(two), tri-(three), tetra-(four). 5.Number and number (,) number and alphabet(-) 6.Alkenes containing two and three double bonds are known as alkadienes and alkatrienes respectively .(replace the ending ne from the name of the corresponding alkanes with diene and triene respectively .
EXAMPLE ON NAMING THE ALKENESH HCH H H H
H-C-C-C-C=C-C-HH HH H H H C H
HStep 1 longest continuous chain contains -C=C- , 7 C atoms . - base name : heptene
H HCH H H
methylH
H-C-C-C-C=C-C-HH HH H H H C H H Step 2 identify substituent group -substituent group : methyl
H HCH H H H
methyl
H-C-C-C-C=C-C-HH HH H H H C H H Step 3 number the carbon atom in the main chain . How??? From right - double bond on second C , methyl on the fourth C atom .
H HCH H H H
methyl
H-C-C-C-C=C-C-HH HH H H H C H H From left- double bond on fifth C , methyl on the fourth C atom . Which one is the correct way ?? .
Name of the alkene : 4-methylhept-2-ene
Did alkenes shows isomerism ???
Let us draw the isomers for C4H8 and C5H10.
Please name all the isomers according to the IUPAC nomenclature .
PHYSICAL PROPERTIES
What do you think of the physical properties of alkenes?? Are they similar to alkanes??Discuss in your groups and comes out with conclusion on : i) Physical state at room temperature ii)Melting and boiling point iii)Density iv)Solubility in water and organic solvent v)Electrical conductivity
CHEMICAL PROPERTIES OF ALKENES
Alkenes-unsaturated hydrocarbons with -C=C- as functional group. -these make alkenes more reactive than alkanes. -Reactions of alkenes are mainly addition reactions to the double bond
REACTION 1 : COMBUSTION OF ALKENESi) Sufficient or excess O2 (complete combustion) Alkenes + O2 CO2 + H2O + heat ii) Not enough O2 (incomplete combustion) Alkenes + O2 CO + H2OOR
Alkenes + O2 C + H2O
Comparison the sootiness of the flame between alkenes and alkanes with the same number of carbon atoms
Percentage of = 5(12) x 100 carbon in pentane 5(12) +12(1) (C5H12) = 83.33%
= 5(12) Percentage of x 100 carbon in pentene 5(12) +10(1) (C5H10) = 85.71%Because of % of carbon in pentene is higher than in pentane , therefore pentene burns with a more sooty flame compared to pentane
REACTION 2 : ADDITION REACTIONS-functional group : -C=C-these make alkenes more reactive than alkanes. -Addition reaction is a reaction in which a molecule adds to the two carbon,C atoms of a double bond .
Addition reaction in general :Chemical unsaturated compounds
-C=C- + X-Y
-C-Csaturated
X Y
i) Addition of hydrogen gas , H2(hydrogenation)
-C=C- + H-H
-C-CHH
Condition: -Alkene vapour and hydrogen gas -passed over a catalyst (Pt/Ni)-heated to 1800C Eg: C2H4 + H2 C3H6 + H2 Alkenes
C2H6C3H8 alkanes
ii) Addition of halogen , X2(halogenation)-C=C- + X-X -C-CX X
X= Cl , Br Condition: -alkene reacts with Cl2/CCl4 and Br2/CCl4 -room temperature-the product is haloalkane Eg: C2H4 + Cl2 C3H6 + Br2 Alkenes C2H4Cl2 C3H6Br2 haloalkanes
When X2 = Br2
-Useful as a test for unsaturation (the presence of double or triple bonds)-useful to distinguish alkenes and alkanes CH3CH=CH2 + Br2 CH3CHBrCH2Br
Observation : The colour changes from reddish-brown to colourless CH3CH2CH3 + Br2dark
no reaction
Observation : reddish-brown colour of bromine remains unchanged
iii) Addition of hydrogen halide , HX-C=C- + H-X -C-CHX
X= Cl , Br Condition: -alkene reacts with HCl and HBr -room temperature-the product is haloalkane Eg: C2H4 + HCl C3H6 + HBr Alkenes C2H5Cl C3H7Br haloalkanes
iv) Addition of water, H-OH / hydration-C=C- + H-OH -C-CH OH
Condition: -mixture of alkene with steam -passed over a catalyst (H3PO4)-T = 3000C , P = 60 atm The product is alcohol Eg: C3H6 + HOH C3H7OH
C4H8 + HOH
C4H9OH
v) Addition of acidified KMnO4 solution-C=C- + [O] + H2O -C COH OH
Condition: -alkene reacts with KMnO4 solution acidified with sulphuric acid -room temperatureThe product is alcohol (alkanediol) Eg: C3H6 + [O] + H2O C2H4 + [O] + H2O C3H6(OH)2 C2H4(OH)2
-Useful as a test for unsaturation (Baeyer test) the presence of double or triple bonds) -useful to distinguish alkenes and alkanesCH3CH=CH2+ [O] + H2 CH3CH(OH)CH2OH
Observation : The colour changes from purple to colourless CH3CH2CH3 + KMnO4 Observation : no reaction
purple colour of KMnO4 remains unchanged
REACTION 3 : POLYMERIZATION Polymerization-the process of chemically joining small molecules (monomer) to form a polymer
Addition Polymerization-involves combining monomers that have multiple bonds
Condensation Polymerization-involves combining monomers that have at least two functional groups
Polymer is a long chain molecule made up of smaller molecules called monomers that are join end to endAlkenes forms polymers by undergoes addition polymerization
H H T = 3000C n H-C=C-H P = 100atm
H H
C CH H n
Comparison Between Alkanes And Alkenes SIMILARITIES -physical properties ALKANESDIFFERENCES Functional group Type of reaction General formula Reaction with Br2/CCl4 Reaction with KMnO4/H+Combustion(no. of C is the same)
ALKENES
Type of compound
-General formula :
CnH2n+1OH ,n =1,2,3,..
-functional group : -OH , hydroxyl -each member of alcohols contains at least one OH group . -Naming use IUPAC nomenclature - alcohols are named by substituting the ending e in the name of the corresponding alkane with ol -ending ol : indicates the compound is a member of alcohols family
NAME OF STRAIGHT CHAIN ALCOHOLSNumber of C atoms1 alkanes methane ethane propane butane
IUPAC namemethanol ethanol propanol butanol
23 4
56
pentane hexane heptaneoctane nonane
pentanolhexanol heptanol octanol nonanol decanol
78 9
10
decane
Steps :
IUPAC NOMENCLATURE
1.Find the longest continuous carbon chain containing the hydroxyl group (main chain). use the name of this chain as the base name of the compound. 2.Identify the substituent group 3.The location of the hydroxyl group is shown by a number. The numbering starts from the end of the main chain that gives a lower number to the C-OH. (also state the location of substituent and -OH group)
4.When two or more substituents are present ,list them in alphabetical order . Use prefix di-(two), tri-(three), tetra-(four).5.Number and number (,) number and alphabet(-) 6.Alcohols containing two and three hyrroxyl group are known as alkanediol and alkanetriol respectively .(add diol and triol)
EXAMPLE ON NAMING THE ALCOHOLSH HCH H H H H OH
H-C-C-C-C- C-C-HH HH H H H C H
HStep 1 longest continuous chain contains -OH , 7 C atoms . - base name : heptanol
H
HCH H H H H OH H HH H H H C H H
methyl
H-C-C-C-C- C-C-H
Step 2 identify substituent group -substituent group : methyl
H
HCH H H H H OH H HH H H H C H H
methyl
H-C-C-C-C- C-C-H
Step 3 number the carbon atom in the main chain . How??? From right C-OH on C 1, methyl on the C 4 .
H
HCH H H H H OH H HH H H H C H H
methyl
H-C-C-C-C- C-C-H
From left- C-OH on C 7 , methyl on the C 4 Which one is the correct way ?? .
Name of the alcohol : 4-methylheptan-1-ol
Did alcohols shows isomerism ???
Let us draw the isomers for C3H7OH , C4H9OH and C5H11OH
Please name all the isomers according to the IUPAC nomenclature .
Physical Properties
a) Melting and Boiling Point* Low boiling points and melting points because Van der Waals forces between molecules are weak
Boiling points and melting points increase as number of carbon atoms per molecule increases. Then, size of molecules increases (molecular mass increases)Forces between molecules (van der Waals forces) are stronger More heat energy is needed to overcome the forces
b) Physical State at Room TemperatureC1 C12 >C13 : liquid : solid
c) Solubility* Simple alcohols (first 3 members) soluble in water. Why??? Alcohols molecules form hydrogen bond with water molecules (because it has hydroxyl group) .
d) Density* The density of the alcohols increases with increasing number of carbon atoms per molecule , BUT is less than water.
e) Electrical Conductivity
Do not conduct electricity because : alcohols are covalent compounds, do not have free moving ions but are made up of molecules
PHYSICAL PROPERTIES OF ETHANOL Colourless liquid at room temperature
Completely miscible with water Has low boiling point (780C) Highly volatile Density < H2O (0.79 gml-1)
MAKING ALCOHOLS (especially Ethanol)
Industry
laboratory
Fermentation Hydration of reaction of ethene glucose How??? How??? -ethene vapour mix -fermenting starchy together with steam . or sugary substances -T=3000C -catalyst : zymase -P = 60 atm -catalyst : phosphoric acid enzyme(in yeast) C6H12O6 2 C2H5OH C2H4 + HOH C2H5OH + 2 CO2
CHEMICAL PROPERTIES OF ALCOHOLS --OH (hydroxyl) as a functional group. REACTION 1 : COMBUSTION OF ALKENES
i) Sufficient or excess O2 (complete combustion)Alcohol + O2 CO2 + H2O + heat ii) Not enough O2 (incomplete combustion) Alcohol + O2 CO + H2OOR
Alcohol + O2 C + H2O
ii) Oxidation of alcohols
**apparatus
General reaction : RCH2OHAlcohol
RCOOHCarboxylic acid
Condition: -add acidified potassium dichromate(VI) solution into alcohols and heat the mixtureOxidising agent Observation K2Cr2O7/H+ Orange solution turns to green solution KMnO4/H+ Purple colour of the solution is decolourised
Eg: CH3CH2OH + 2[O]CH3CH2CH2OH + 2[O]
CH3COOH + H2OCH3CH2COOH + H2O
Alcohols
carboxylic acid
iii) Dehydration of alcohols
**apparatus-C=C- + H2OalkeneChemical test to identify this product??
-C-C-
Dehydrating agents
Alcohol
H OH
Condition:
1. Concentrated sulphuric acid ,H2SO4 at 1800C @2. alumina/porcelain chips at 3500C (heated catalyst) @
3. Concentrated phosphoric acid ,H3PO4 at 3500C
CH3CH2OH CH3CH2CH2OH
CH2=CH2 + H2O CH3CH=CH2 + H2O
Alcohols
alkenes
iv) Esterification reaction
**apparatus
Concentrated O O sulphuric acid R-C-OH + ROH R-C-OR + H2O Ester Carboxylic Alcohol acid How can we identify
Condition:
this product??
Catalyst : concentrated sulphuric acid
Write down the chemical equation for reaction :
1. Ethanoic acid and ethanol 2. propanoic acid and ethanol 3. Ethanoic acid and propanol
-General formula :
CnH2n+1COOH ,n =0 1,2,3,..
-functional group : -COOH , carboxyl -each member of carboxylic acids contains at least one COOH group . -Naming use IUPAC nomenclature - carboxylic acids are named by substituting the ending e in the name of the corresponding alkane with oic , continue with acid -ending oic acid : indicates the compound is a member of carboxylic acid family
NAME OF STRAIGHT CHAIN CARBOXYLIC ACIDSNumber of C atoms 1 2 3 4 5 6 7 alkanes methane ethane propane butane pentane hexane heptane IUPAC name methanoic acid ethanoic acid propanoic acid butanoic acid
pentanoic acidhexanoic acid heptanoic acid
89 10
octanenonane decane
octanoic acidnonanoic acid decanoic acid
Steps :
IUPAC NOMENCLATURE
1.Find the longest continuous carbon chain containing the carboxyl group (main chain). use the name of this chain as the base name of the compound. 2.Identify the substituent group 3.The location of the carboxyl group is always number 1. The numbering starts from carboxyl group . (also state the location of substituent group)
4.When two or more substituents are present ,list them in alphabetical order . If theyre same -use prefix di-(two), tri(three), tetra-(four).5.Number and number (,) number and alphabet(-) 6.Carboxylic acid containing two and three carboxyl group are known as dicarboxylic acid and tricarboxylic acid respectively
EXAMPLE ON NAMING THE CARBOXYLIC ACIDS
HHCH H H H H O
H-C-C-C-C- C-C-OHH HH H H C HH
Step 1 longest continuous chain contains -COOH , 7 C atoms . - base name : heptanoic acid
HHCH H H H H O
methyl
H-C-C-C-C- C-C-OHH HH H H C HH Step 2 identify substituent group -substituent group : methyl
HHCH H H H H O H HH H H C H H
methyl
H-C-C-C-C- C-C-OH
Step 3 number the carbon atom in the main chain . How??? From right COOH start no. 1, methyl on the C 4 .
HHCH H H H H O H HH H H C H H
methyl
H-C-C-C-C- C-C-OH
carboxyl
Name of the alcohol : 4-methylheptanoic acid
Did carboxylic acids show isomerism ??? Concept : functional group isomerism ???
Let us draw the isomers for C4H8O2 , C5H10O2 Please name all the isomers according to the IUPAC nomenclature .
Physical Properties
a) Melting and Boiling Point* Boiling points and melting points are higher than that of alkanes with the same number of carbon atoms.(-COOH)
Boiling points and melting points increase as number of carbon atoms per molecule increases. Then, size of molecules increases (molecular mass increases)Forces between molecules (van der Waals forces) are stronger More heat energy is needed to overcome the forces
b) Physical State at Room TemperatureC1 C9 >C10 : liquid : solid
c) Solubility* Simple carboxylic acids (C1-C4) soluble in water. Why??? carboxylic acids molecules form hydrogen bond with water molecules (because it has carboxyl group) . * As number of C atom permolecule increases , solubility decreases . Why ???
PHYSICAL PROPERTIES OF ETHANOIC ACID Clear and colourless liquid at room temperature Very soluble in water Boiling point (1180C)
It has a characteristic smell It tastes sour
Pure ethanoic acid does not contain water , called glacial ethanoic acid
MAKING CARBOXYLIC ACIDS (especially Ethanoic acid / acetic acid)
Oxidation of alcohols
General reaction : RCH2OHAlcohol
**apparatus RCOOHCarboxylic acid
Condition: -add acidified potassium dichromate(VI) solution into alcohols and heat the mixtureOxidising agent Observation
K2Cr2O7/H+ KMnO4/H+
Orange solution turns to green solution Purple colour of the solution is decolourised
CH3CH2OH + 2[O]CH3CH2CH2OH + 2[O]
CH3COOH + H2OCH3CH2COOH + H2O
CHEMICAL PROPERTIES OF CARBOXYLIC ACIDS
--COOH (carboxyl) as a functional group. REACTION 1 : REACTIONS WITH BASES (Neutralization reaction) Dissociation of carboxylic acid :
RCOOH
RCOO- + H+
Carboxylic acid + BASE Salt + H2O
Eg. CH3COOH + NaOH CH3COONa + H2OSodium ethanoate
CH3COOH + NH3 CH3COONH4
ammonium ethanoate
REACTION 2: REACTIONS WITH METALSCarboxylic acid + METAL Salt + H2 Eg. 2CH3COOH + Mg (CH3COO)2Mg + H2magnesium ethanoate
2CH3CH2COOH + Zn (CH3CH2COO)2Zn + H2zinc propanoate
REACTION 3: REACTIONS WITH METAL CARBONATE
Carboxylic acid + METAL CARBONATE Salt + H2O + CO2 Eg. 2CH3COOH + CaCO3 (CH3COO)2Ca + H2O + CO2Calcium ethanoate
2CH3CH2COOH + Zn (CH3CH2COO)2Zn + H2O + CO2zinc propanoate
4) Esterification reaction
**apparatus
Concentrated O O sulphuric acid R-C-OH + ROH R-C-OR + H2O Ester Carboxylic Alcohol acid How can we identify
Condition:
this product??
Catalyst : concentrated sulphuric acid
Write down the chemical equation for reaction :
1. Ethanoic acid and ethanol 2. propanoic acid and ethanol 3. Ethanoic acid and propanol
-General formula :
CnH2n+1COOCmH2m+1 , n =0 1,2,3,.. ,m=1,2,3,..
-functional group : -COOR , carboxylate
-each member of esters contains at COOR group.-Naming use IUPAC nomenclature - the name of esters is derived from the name of alcohol and carboxylic acid that reacted together to produce it.
1.Alkyl from alcohol continue with carboxylic acid . 2.Replace oic with oate
ESTERS SIMPLE ESTERS - found in fruits and flowers - Responsible for the fruity smells and pleasant fragrances - More volatile compare to complex esters COMPLEX ESTERS
- found in animal fats and vegetable oil- Do not produce the familiar pleasant smells of the simple esters - less volatile compare to simple esters
Esterification reactionConcentrated O O sulphuric acid R-C-OH + ROH R-C-OR + H2O Ester Carboxylic Alcohol acid How can we identify
Condition:CH3COOH + CH3CH2OH Ethanoic acid Ethanol
this product??
Catalyst : concentrated sulphuric acid
CH3COOCH2CH3 + H2O Ethyl ethanoate
***Gives examples
HYDROLYSIS OF ESTERS(need to reflux) Esters can be hydrolysed to carboxylic acid with the use of acid or base as catalyst Alkaline hydrolysis also known as saponification
Write down the chemical equation for reaction :O R-C-OR + H-OH H+ O R-C-OH + ROH
O O OHR-C-OR + H-OH R-C-O+ ROH Also known as saponification reaction
Oils and fats are esters . What the differences between oils and fats ??? Property SourcePhysical state at Room temperature
Oils
Fats
Found in plants Found in animals LiquidSolid or semi-solidMore than 200C
Melting point
Less than 200C
1. Oils and fats are esters formed from carboxylic acids called fatty acids and alcohol called 1,2,3-propanetriol/ propane-1,2,3-triol2. A fatty acid is a carboxylic acid that has a long chain of about 10 to 20 carbon atoms with one carboxyl group . 3. Eg of fatty acids: palmitic acid(C15H31COOH), stearic acid(C17H35COOH), linoleic acid(C17H31COOH), oleic acid(C17H33COOH) 3. 1,2,3-propanetriol or glycerol is an alcohol that has three hydroxyl groups .
The esterification reaction between fatty acids and glycerols produces oils and fats . Fatty acid + glycerolOleic acid + glycerol
Oil or fatTriolein/ glyceryl trioleate Trilinolein/ glyceryl trilinoleate
+ H2O+ H2O
linoleic acid
+ glycerol
+ H2O
Show the reaction !!!!!
FatsSaturated fats- fat that has more saturated fat molecules compared to unsaturated fat molecules - A molecules of fat is saturated if its fatty acid chains do not have any double bonds between carbon atoms .
Unsaturated fats- fat that has more unsaturated fat molecules compared to saturated fat molecules - A molecules of fat is unsaturated if its fatty acid chains have double bonds between carbon atoms . (monounsaturated and polyunsaturated)
What the differences between saturated and unsaturated fats ??? PropertyProportion of moleculesPhysical state at Room temperature Unsaturated fats Saturated Fats Higher proportion Higher proportion of unsaturated fat of saturated fat molecules molecules
Liquid Less than 200C
Solid or semi-solid More than 200C
Melting point
Source
Found in plants Found in animals
Converting unsaturated fats to saturated fats -by using hydrogenation reaction -carried out by passing hydrogen gas, through the unsaturated fat at 1500C to 2000C . A catalyst such as nickel is required. Concept :
-C=C- + H2 -C-C-
Check (revision book )- process to convert an oil to a fat ( such as margarine )
Please do some studies on the effects of fats on health ,industrial production of palm oil , palm oil in food production , research on oil palm in Malaysia and the palm oil industry in Malaysia
POLYMERS Large molecules formed from smaller molecules called monomers
Natural polymers
Synthetic polymers
Starch
protein
How can we convert to glucose ??
Natural rubber
nylon
PVC
Polyetheneperspex
- Natural rubber contains polyisoprene molecules- Monomer is isoprene (2-methylbut-1,3-diene) -Isoprene undergoes addition polymerisation to form polyisoprene molecules
Please write chemical equation shows the formation of polyisoprene from isoprene
Properties of natural rubber Property Elasticity Resistance to oxidation DescriptionNatural rubber is elastic.It will return to its original after you stretch it Natural rubber is easily oxidised by oxygen. O2 adds to the -C=CNatural rubber cannot withstand heat. High T - soft and sticky , Low T-becomes hard and brittle
Effect of heatEffect of solvent
Acidic and alkaline solvents can attack and destroy natural rubber.
COAGULATION OF LATEXmade up of a protein membrane that surrounds many rubber molecules Negative charges are found on the surface of the membrane Negatively-charge rubber particles repel each other, preventing themselves from combining and coagulating
LATEX -is a
colloid (mixture of rubber particles and water)
The effect of adding acid into the latex LATEXAdding acidH+ ions from an acid neutralise the negative charges found on the surface of the membrane These neutral rubber particles collide with each other Outer membrane of the rubber particles break up
Rubber molecules clump together .the latex has coagulatedRubber molecules are set free
The effect of adding alkali (NH3 solution) into the latex LATEXAdding NH3 solutionOH- ions from an alkali neutralise the H+ ions produced by lactic acid as a result of bacterial attack on protein
The rubber particles repel each other, preventing themselves from combining and coagulating
The rubber particles remain negatively charged
The effect of exposing the latex to the surrounding air LATEXLeft overnightH+ ions produced by lactic acid as a result of bacterial attack on protein neutralise the negative charge of the membrane of the rubber particles
Rubber molecules clump together .the latex has coagulated Rubber molecules are set free
These neutral rubber particles collide with each otherOuter membrane of the rubber particles break up
Vulcanisation of rubber
Definition : the process of chemically treating natural rubber with sulphur,S-This process convert raw rubber into a tough useful product (vulcanised rubber-rubber with sulphur cross-links between rubber molecules ). -in industry heating the mixture of natural rubber and sulphur , ZnO as catalyst. -in lab dipped the natural rubber in the solution of disulphur dichloride (S2Cl2) in methylbenzene
Vulcanisation of rubberDuring the vulcanisation processAdding S to the rubber molecules S react with C=C in rubber molecules S atoms form crosslinks between adjacent chains of rubber polymer at the C=C These crosslinks prevent rubber molecules from sliding too much when stretched.
Mr rubberMelting pointMore tougher and can withstand heat
Vulcanised rubber cannot easily oxidised by O2
The formation of cross-links decreases the C=C in the rubber molecules