Organic Chemistry

374 CHAPTER 10 Substitution Reactions of Alkyl Halides

PROBLEM 8 SOLVED

What product is obtained when ethylamine reacts with excess methyl iodide in a basic so-

lution of potassium carbonate?

SOLUTION Methyl iodide and ethylamine undergo an reaction. The product of the

reaction is a secondary amine, which is predominantly in its basic (neutral) form since the

reaction is carried out in a basic solution. The secondary amine can undergo an reac-

tion with another equivalent of methyl iodide, forming a tertiary amine. The tertiary amine

can react with methyl iodide in yet another reaction. The final product of the reaction

is a quaternary ammonium iodide.

PROBLEM 9

a. Explain why the reaction of an alkyl halide with ammonia gives a low yield of primary

amine.

b. Explain why a much better yield of primary amine is obtained from the reaction of an

alkyl halide with azide ion followed by catalytic hydrogenation. (Hint:An alkyl

azide is not nucleophilic.)

PROBLEM 10

Using the values listed in Table 10.3, convince yourself that each of the reactions on

page 372 proceeds in the direction shown.

PROBLEM 11

What is the product of the reaction of ethyl bromide with each of the following nucleophiles?

a. b. c. d.

PROBLEM 12

The reaction of an alkyl chloride with potassium iodide is generally carried out in acetone

to maximize the amount of alkyl iodide that is formed. Why does the solvent increase

the yield of alkyl iodide? (Hint:Potassium iodide is soluble in acetone, but potassium

chloride is not.)

CH 3 OH - N 3 (CH 3 ) 3 N CH 3 CH 2 S-

pKa

CH 3 CH 2 CH 2 NNN− CH 3 CH 2 CH 2 NH 2 +N 2

−N 3

CH 3 CH 2 CH 2 Br

H 2

an alkyl azide Pt

+

(-N 3 ),

CH 3 CH 2 NH 2 CH 3 CH 3 CH 2 NHCH 3

I−

+

+ +

CH 3 CH 2 NHCH 3

CH 3 CH 2 NH 2 + CH 3 I

I−

CH 3 I

CH 3 CH 3 CH 3

CH 3

I−

K 2 CO 3

CH 3 CH 2 NCH 3 CH 3 CH 2 NCH 3

CH 3 I K 2 CO 3

SN 2

SN 2

SN 2

CH 3 CH 2 NH 2 + CH 3 I?

K 2 CO 3

excess

Henri Louis Le Châtelier
(1850–1936)was born in France.
He studied mining engineering and
was particularly interested in learning
how to prevent explosions. His interest
in mine safety is understandable,
considering that his father was
France’s inspector-general of mines.
Le Châtelier’s research into
preventing explosions led him to study
heat and its measurement, which in
turn focused his interest on
thermodynamics.