Recitation
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Chapter 22 Recitation
Please note that these exercises are not a substitute for but an addition to the homework
assignment
1. Give the hybridizations of the orbitals on the numbered carbon atoms in the following molecules and
give the bond angles for the bonds around them. Which one(s) exhibit(s) cis-trans isomerism?
H H H
H C C3 H H C C C CH3 H3C C C H
2 1
H H
H H H
(A) (B) (C)
C1 sp3 109 º
C2 sp2 120 º
C3 sp 190 º
2. Peroxypropionyl nitrate (PPN) is an eye irritant found in smog. Give the hybridizations of the orbitals on
the numbered atoms in its structure and the bond angles. The octet rule is obeyed.
H O O
5
H3C C C O O N O
6 4 3 2 1
H
O1 , N2 O3 and C6 are sp3 hybridized and the bond angles around them are 109 º .
C4 and O5 are sp2 hybridized and the bond angles around them are 120 º .
3. Give the structural formulas of
a. the three-carbon alcohol with an OH group at the end of the chain.
H
H H
H C C C OH
H H H
b. the three-carbon carboxylic acid.
H
H
H C C C OH
H H
O
c. the ester formed when these two compounds react.
H
H H H H
H C C C O C C C H
H H H H
O H
4. Draw and name all the structural isomers of dichroropropane (C3H6Cl2).
H
H H
H C C C Cl
H
Cl H
1,2-dichloropropane
H
H H
H C C C Cl
H H
Cl
1,1-dichloropropane
H
Cl H
H C C C H
H
Cl H
2,2-dichloropropane
H
H H
H C C C Cl
Cl H
1,3-dichloropropane H
5. Draw and name all the isomers of dichloroethene (C2H2Cl2).
H Cl Cl Cl
Cl H
C C C C C C
H Cl H H H Cl
1,1-dichloroethene cis-dichloroethene tran-dichloroethene
6. Each of the following names is wrong. Draw structures based on these names then give the correct
names.
H H H H H
H
H C C C C C C H
H H H CH3 H H
(a) 4-methylhexane 3-methylhexane
H H H H H
H C C C C C H
H H H H
C2H5
3-methylhexane
(b) 2-ethylpentane
CH3
(c) 2-methylcyclohexane methylcyclohexane
CH3
CH3 CH2 C CH CH2CH2 CH2 CH3
CH3C2H5
(d) 3,3-methyl-4-ethyloctane 4-ethyl-3,3-dimethyloctane
7. Draw structures from the following names, and determine which compounds are optically active. An
optically active compound has a structure that is not super-imposable with the structure of a compound
that is a mirror image of it. An organic compound containing on or more C atoms with sp3 and attached
to four different atoms or groups of atoms exhibits optical isomerism.
(a) 3-bromohexane
(b) 3-chloro-3-methylpentane
(c) 1,2-dibromo-2-methylbutane.
Ignore this question as you have not taken optical activity in organic compounds although I give the answer
below.
H H H H H H
H C C C C C C H
H
H H H H
Br
This compound is optically active. The hybridization
of the third C from the left is sp3 and four different groups are attached to it. These are H, Br,
C2H5 and C3H7.
H H CH3 H H
H C C C C C H
H
H H H
Cl
This compound is not optically active. There is no C with four
different groups attached to it.
H CH3 H H
H C C C C H
H
Br Br H
This compound is optically active. The second C from the left is
attached to four different groups. These are CH2Br, Br, CH3 and C2H5.
8. Which of the following structures exhibit geometric isomerism? Draw and name the two isomers in
each case.
(a)
CH3 CH2 CH CH CH3
CH3 CH3 C2H5
H
C C C C
H C2H5 H H
Trans isomer Cis isomer
(b)
CH CH CH3
CH3
H H H
C C C C
H
CH3
Trans isomer Cis isomer
(c)
CH3
CH3
CH3 CH C CH CH2 CH3
This compound does not exhibit cis-trans isomerism as one of the C atoms on the double bond has two
identical groups (CH3 groups) on it.
9. Which compounds exhibit geometric isomerism? Draw and name the two isomers in each case.
(a) propene (b) 3-hexene (c) 1,1-dichloroethene (d) 1,2-dichloroethene
CH3
H
C C
H H does not exhibit cis-trans isomerism. Two H's on the same C atom.
(a)
H C2H5 C2H5 C2H5
C C C C
C2H5 H H H
(b)
Trans Cis
Cl H
C C
Cl H Does not exhibit cis-trans isomerism each C is bonded to two identical atoms
(c)
Cl H H H
C C C C
H Cl Cl Cl
(d)
Trans Cis
10. Write down the structures of the primary, secondary and tertiary isomers of the amine C4H9NH2.
NH2
NH2
CH3 CH2 CH2 CH2 NH2 CH3 CH2 CH CH3 CH3 CH3
C
CH3
Primary secondary tertiary
11. What product is formed by:
(a) The oxidation of a primary alcohol such as C2H5OH.
O
CH3C
H
(b) The oxidation of the seconday propyl alcohol. CH3CH(OH)CH3.
CH3 C CH3
O
(c) The oxidation of acetaldehyde CH3CHO.
OH
CH3 C
O
(d) The reaction between methyl alcohol CH3OH and acetic acid CH3COOH.
OCH3
CH3 C
O
12. Which of the following will undergo an addition reaction?
(a) alkene (b) alkane (c) benzene (d) an alcohol
13. Familiarize yourself with the two main ways of obtaining polymers. Addition polymerization is a chain
reaction initiated by a free radical. Elimination reaction involves the removal a small molecule from
two molecules for each extension of the chain. When such molecule is water as is commonly the case
elimination reactions are referred to as condensation reactions. Many elimination polymers are called
Polymers are called polyesters because the repeating unit is an ester formed by eliminating water from
an alcohol and a carboxylic acid. Familiarize yourself with the many uses of polymers.
