Here you’ll find the answers to the Tasks that are embedded in the current Introduction to Organic Chemistry Notes.
UNIT 01 – Nomenclature
Task 1a
Alkanes
1.
(i) 2,2-dimethylbutane
(ii) 2,3,5-trimethyl-4-propylheptane
(iii) 3,3-diethylhexane
(iv) 2,4-dimethylpentane
(v) 4-ethyl-2,2,5-trimethylheptane
2.
(i)
(ii)
(iii)
(iv)
(v)
Alkenes & Alkynes
3.
(i) But-1-ene
(ii) But-2-yne
(iii) 4-methylhex-2-yne
(iv) 4-methylpent-2-yne
(v) Buta-1,3-diene
4.
(i)
(ii)
(iii)
(iv)
(v)
Halogen Compounds
5.
(i) 1-iodopentane
(ii) 4-ethyl-3-methyl-nonanoyl bromide
(iii) Bromobenzene
(iv) (chloromethyl)benzene (benzyl chloride)
(v) 2-bromopropane
6.
(i)
(ii)
(iii)
(iv)
(v)
Alcohols
7.
(i) Pentan-3-ol
(ii) 2-methylbutan-2-ol
(iii) 3-bromobutan-2-ol
(iv) 3-phenylbutan-1-ol
(v) 3-nitrophenol
8.
(i)
(ii)
(iii)
(iv)
(v)
Aldehydes & Ketones
9.
(i) Butanal
(ii) 3-methylbutan-2-one
(iii) 2-methylpropanal
(iv) 3-methylbutan-2-one
(v) 3-phenylpropanal
10.
(i)
(ii)
(iii)
(iv)
(v)
Carboxylic Acids & Derivatives
11.
(i) Propanoic acid
(ii) 3-hydroxypentanoic acid
(iii) 2,2-dimethylpropanoic acid
(iv) 2-methylpropanoyl chloride
(v) 2-phenylpropanoic acid
12.
(i)
(ii)
(iii)
(iv)
(v)
Aromatics
13.
(i) (chloromethyl)benzene
(ii) 1,2-diethylbenzene
(iii) 4-bromophenol
(iv) 2-chlorotoluene
(v) 2-nitrobenzoic acid
14.
(i)
(ii)
(iii)
(iv)
(v)
Nitrogen Compounds
15.
(i) propanonitrile
(ii) N-methylaniline
(iii) 2-aminobenozic acid
(iv) N,N-diethylethanamine
(v) 3-phenylbutanonitrile
16.
(i)
(ii)
(iii)
(iv)
(v)
UNIT 02 – Isomerism
Task 2a
1.
2.
Hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane.
3.
Nonanes
2-methylnonane
3-methylnonane
4-methylnonane
5-methylnonane
Pentanes
2,4-dimethyl-3-(1-methylethyl)pentane
3,3-diethyl-2-methylpentane
3-ethyl-2,2,3-trimethylpentane
3-ethyl-2,2,4-trimethylpentane
3-ethyl-2,3,4-trimethylpentane
2,2,3,3,4-pentamethylpentane
2,2,3,4,4-pentamethylpentane
Task 2b
1.
2. IUPAC nomenclature insists that locants be kept as low as possible. As a result, butan-3-ol and butan-4-ol could (and should) be called butan-2-ol and butan-1-ol respectively, when counting from the other end of the chain.
3.
3 isomers; 2-mehylphenol, 3-methylphenol and 4-methylphenol.
4.
1,1-dibromobutane
1,2-dibromobutane
1,3-dibromobutane
1,4-dibromobutane
2,2-dibromobutane
2,3-dibromobutane
1,1-dibromo-2-methylpropane
1,2-dibromo-2-methylpropane
1,3-dibromo-2-methylpropane
Task 2c
1.
2.
Many answers possible here, but perhaps the simplest are pent-1-ene and cyclopentane;
3.
Many answers possible here, but perhaps the simplest are hexanal and hexan-2-one;
Task 2d
The cis isomer. Since a water molecule is eliminated by combining the -OH groups of two acid groups, they must be on the same side of the molecule to facilitate the dehydration reaction.
Task 2e
1.
E
Z
2.
There are no identical groups attached to each of the C atoms of the double bond, that can be grouped as being on the same side (cis) or different sides (trans).
3.
E
Z
Task 2f
1.(a)
(b)
Task 2g
1.
Least stable: Eclipsed with CH3 groups aligned (#4), then
Eclipsed with CH3 and H aligned (#2), then
Staggered with CH3 groups adjacent to one another (gauche) (#1), then
Most stable: Staggered with CH3 groups opposite one another (anti) (#3)
2.
Task 2h
1.
(a) 1,1-dichloropropane, 1,2-dichloropropane, 1,3-dichloropropane, 2,2-dichloropropane
(b) but-1-ene, but-2-ene, 2-methylpropene, cyclobutane, methylcyclopropane
(c) 1-bromobutane, 2-bromobutane, 2-bromo-2-methylpropane, 1-bromo-2-methylpropane
(d) 1-methyl-2,3-dinitro benzene, 1-methyl-2,4-dinitro benzene, 1-methyl-2,5-dinitro benzene, 1-methyl-2,6-dinitro benzene, 1-methyl-3,4-dinitro benzene, 1-methyl-3,5-dinitro benzene
2.
(a) Ethanoic acid, methyl methanoate, hydroxyethanal
(b) cis-Ethene-1,2-diol, trans-Ethene-1,2-diol, Ethene-1,1-diol
(c) Those in (a) are functional group isomers of those in (b)
3.
(a) cis-1,2-dibromoethene, trans-1,2-dibromoethene, 1,1-dibromoethene
(b) chloroethene (no isomers)
4.
(e) They each have a chiral center.
5.
R
UNIT 03 – Mechanisms
No Tasks as yet
UNIT 04 – Reactions
Task 4a
1.
Propan-1-ol and propan-2-ol. (1° and 2° alcohols)
2.
CH3CH2CH2OH + [O] → CH3CH2CHO (propanal) + H2O
CH3CH2CHO + [O] → CH3CH2COOH (propanoic acid)
Color change from orange to green.
CH3CH(OH)CH3 + [O] → CH3COCH3 (propanone) + H2O
Color change from orange to green.
3.
Cr2O72- + 14H+ + 6e– → 2Cr3+ + 7H2O
MnO4– + 8H+ + 5e– → Mn2+ + 4H2O
UNIT 05 – Structure Determination
Task 5a
C5H6O3
Task 5b
1.
Ethanol and propan-2-ol give positive iodoform tests.
2.
Only the pair in (c).
Task 5c
P = Propan-1-ol. Peak at 3300 cm-1 due to O-H group. No carbonyl peak. Peaks around 3000 cm-1 are C-H peaks.
Q = Propanal. Peak at 1750 cm-1 due to the carbonyl group, C=O. No O-H peak. Peaks around 3000 cm-1 are C-H peaks.
R = Propanoic acid
Source: SDBSWeb
Task 5d
1.
91 = [C6H5CH2]+
92 = [C6H5CH3]+
93 = [13C6H5CH3]+
2.
29 =[CH3CH2]+
43 = [C=OCH3]+
72 = [CH3CH2C=OCH3]+
UNIT 06 – Synthesis
Task 6a
1.
90.5%
2.
80.1%