The following problems are selected from the book “organi chemistry” (L. G. Wade, 5th Ed).
1-37 Draw the important resonance forms to show the delocalization of charges in the following ions.
(a)
O
H3C C CH2
(b)
(d)
(e)
(g)
(h)
O
H C CH CH CH2
(c)
CH2
NH
(f)
O
(i)
CH3 CH CH CH CH CH CH3
O
O
(j)
CH3 CH CH CH CH CH2 CH2
Answers:
（a）
O
H3C C CH2
（b）
O
H C CH CH CH2
O
H3C C CH2
O
H C CH CH CH2
O
H C CH CH CH2
CH2
（c）
CH2
CH2
CH2
CH2
（d）
O
O
O
（e）
O
O
NH
（f）
NH
NH
（g）
O
O
O
(h)
O
O
(i)
O
CH3 CH CH CH CH CH CH3
CH3 CH CH CH CH CH CH3
CH3 CH CH CH CH CH2 CH2
CH3 CH CH CH CH CH CH3
CH3 CH CH CH CH CH2 CH2
(j)
CH3 CH CH CH CH CH2 CH2
CH3 CH CH CH CH CH2 CH2
1-41 For each pair of ions, determine which ion is more stable. Use resonance forms for ordering them as
you do.
（a）
CH3 CH CH3
（b）
CH2 CH CH CH3
（c）
H2C CH3
or
CH3 CH OCH3
or
CH2 CH CH2 CH2
H2C C N
CH2
（d）
（e）
or
CH2
or
H3C N CH3
H3C C CH3
or
H3C CH CH3
H3C C CH3
Answers:
（a）
second
CH3 CH OCH3
（b）
first
CH2 CH CH CH3
（c）
second
H2C C N
（d）
first
（e）
first
CH2
H3C N CH3
H3C C CH3
CH3 CH OCH3
CH2 CH CH CH3
H2C C N
CH2
H3C N CH3
H3C C CH3
1-42
Rank the following species in order of increasing acidity.
NH3
H2SO4
CH3OH
Answer: NH3 < CH3OH < CH3COOH < H2SO4
CH3COOH
1-43
Rank the following species in order of increasing basicity.
CH3OCH3COOH CH3COONaOH
NH2-
HSO4-
Answer: HSO4- < CH3COOH < CH3COO- < NaOH < CH3O- < NH21-47 Methyllithium (CH3Li) is often used as a base in organic reactions.
(a) Predict the products of the following acid-base reaction.
CH3 CH2 O H
H3C Li
(b) What is the conjugate acid of CH3Li? Would you expect CH3Li to be a strong or a weak base?
Answers:
（a）
（b）
CH3 CH2 O H
CH3Li
H3C Li
CH3CH2OLi
CH4
CH4
CH3Li is a strong base.
acid
base
2-30 Predict the hybridization and geometry of the carbon and nitrogen atoms in the following ions. (hint:
resonance)
(a)
O
H3C C CH2
(b)
NH2 CH CH CH2
Answers:
（a）
O
H3C C CH2
O
H3C C CH2 (平面三角形)
sp2
sp2
（b）
NH2 CH CH CH2
NH2 CH CH CH2
NH2 CH CH CH2 (sp2 平面三角形)
2-39 N-methylpyrrolidine has a boiling point of 81°C, and piperidine has a boiling point of 106°C.
(a) Explain this large defference (25°C) in boiling point for these two isomers.
(b) Tetrahydropyran has a boiling point of 88°C, and cyclopentanol has a boiling point of 141°C.
These two isomershave a boiling point dofference of 53°C. Explain why the two oxygen-containing
isomerx have a much larger boiling point difference than the two amine isomers.
N CH3
N H
N-methylpyrrolidine , bp 81°C
O
tetrahydropyran, bp 88°C
Answers:
piperidine, bp 106°C
OH
cyclopentanol, bp 141°C
（a）
（b）
N CH3
O
无分子间氢键,
无分子间氢键,
N H
有分子间氢键
OH 有分子间氢键，氢键能比 N-H—N 键能大。