Chemistry 11 (HL)
Unit 7 - IB Topics 10.5 and 20.2
Organic Chemistry
Halogenoalkanes - Practice Problems
1.
Which reaction type is typical for halogenoalkanes?
A.
nucleophilic substitution
B.
electrophilic substitution
C.
electrophilic addition
D.
nucleophilic addition
2.
What is the reaction type when (CH3)3CBr reacts with aqueous sodium
hydroxide to form (CH3)3COH and NaBr?
A. Addition
B. Elimination
C. SN1
D. SN2
3.
A halogenoalkane reacts with a nucleophile to produce propanamine. What is
the nuclelophile?
A. hydroxide ion
C. cyanide ion
4.
What is the same about the reaction of bromoethane with water and of
bromoethane with dilute aqueous sodium hydroxide?
A.
B.
C.
D.
5.
B. amine ion
D. ammonia
Both produce ethanol at the same rate.
Both produce ethanol.
Both undergo SN1 reactions.
Both involve hemolytic fission of the carbon-bromine bond.
When 2-bromopropane undergoes nucleophillic substitution with cyanide ion, the
product that forms is:
A. 2-cyanopropane
C. 2-methylpropamine
B. butanenitrile
D. 2-methylpropanenitrile
6.
What is the reaction type when (CH3)3CBr reacts with aqueous sodium
hydroxide to form (CH3)3COH and NaBr?
A.
Addition
B.
Elimination
C.
SN1
D.
SN2
7.
When 1-bromobutane is added to the following solutions of potassium hydroxide,
which would give the greatest yield of but-1-ene?
solvent
A
B
C
D
8.
ethanol
ethanol
water
water
concentration
(M)
5
0.5
5
0.5
temperature
(ºC)
70
40
40
70
In the elimination reaction of 1-bromethane to produce ethene, the hydroxide
ions acts as:
A. nucleophile
C. a reducing agent
B. an oxidizing agent
D. a base
p. 1
Chemistry 11 (HL)
9.
10.
Unit 7 - IB Topics 10.5 and 20.2
–3
The hydrolysis of 2-iodo-2-methylpropane by 0.10 mol dm KOH(aq) to form
2-methylpropan-2-ol is an example of nucleophilic substitution.
Give equations to illustrate the SN1 mechanism for this reaction. (2)
The molecular formula C4H9Br represents four structural isomers, all of which
can undergo nucleophilic substitution reactions with aqueous sodium hydroxide.
An equation to represent all these reactions is
C4H9Br + NaOH  C4H9OH + NaBr
a)
Explain what is meant by the term nucleophilic substitution. (2)
b)
The main mechanism for a tertiary halogenoalkane is SN1. Give the
equations for this substitution reaction of the tertiary isomer of C4H9Br.
Show the structures of the organic reactant and product and use curly
arrows to show the movement of electron pairs. (4)
c)
The main mechanism for a primary halogenoalkane is SN2. Give the
mechanistic equation for this substitution reaction of the straight-chain
primary isomer of C4H9Br, showing the structures of the organic reactant
and product, and using curly arrows to show the movement of electron
pairs. (4)
p. 2
Chemistry 11 (HL)
d)
11.
Unit 7 - IB Topics 10.5 and 20.2
Give a structural formula for the secondary isomer and for the other
primary isomer. State the name of each isomer. (4)
Write equations to show the mechanisms of the following reactions. In each
case, show the structure of the intermediate and organic product, and use curly
arrows to show the movement of electron pairs.
(i)
the reaction between KOH and CH3CH2CH2CH2Cl.
(ii)
the reaction between KOH and (CH3)3CCl. (2)
(3)
p. 3
Chemistry 11 (HL)
12.
13.
Unit 7 - IB Topics 10.5 and 20.2
The following transition state is formed during the reaction of a halogenoalkane
with aqueous sodium hydroxide:
a)
Deduce the structure of the halogenoalkane. Classify it as primary,
secondary or tertiary, giving a reason for your choice. (2)
b)
The mechanism of this reaction is described as SN2. Explain what is
meant by the symbols in SN2. Predict a rate expression for this reaction.
(3)
c)
The same halogenoalkane reacts with sodium hydroxide by an SN1
mechanism. Deduce the structure of the intermediate formed in this
reaction. (1)
2-bromobutane can be converted into butan-2-ol by a nucleophilic substitution
reaction. This reaction occurs by two different mechanisms.
(i)
Give the structure of the transition state formed in the SN2 mechanism.
(2)
(ii)
Write equations for the SN1 mechanism.
(2)
p. 4
Chemistry 11 (HL)
14.
Unit 7 - IB Topics 10.5 and 20.2
Secondary halogenoalkanes can undergo nucleophilic substitution reactions by
both SN1 and SN2 mechanisms. The mechanism showing the formation of the
transition state in the reaction between 2-bromobutane and potassium hydroxide
can be represented as follows.
a)
Identify the type of mechanism shown. (1)
b)
State and explain how the following changes would alter the rate of the
reaction by this mechanism.
(i)
using water instead of potassium hydroxide. (2)
(ii)
using bromoethane instead of 2-bromobutane. (2)
15.
Identify the halogenoalkane and nucelophile needed to form butan-2-amine. Write
the equation for the reaction. Identify the conditions.
16.
Identify the halogenoalkane and nucelophile needed to form ethanenitrile. Write the
equation for the reaction. Identify the conditions.
p. 5
Chemistry 11 (HL)
17.
18.
Unit 7 - IB Topics 10.5 and 20.2
a)
Write the balanced equation for the conversion of 1-chlorobutane to
butanamine.
b)
Identify the type of mechanism used.
c)
Draw the mechanism using structural formulas and curly arrows.
a)
Draw the structural formula of ethanenitrile.
b)
i) Identify two reactants which could be used to prepare this
compound.
ii) State the balanced equation for this reaction.
c)
Use diagrams to show the mechanism for the formation of this
compound.
p. 6
Chemistry 11 (HL)
Unit 7 - IB Topics 10.5 and 20.2
19.
State the conditions you would use and the mechanism for the reaction that would
convert CH3CH2CH2CH2Br into CH3CH2CHCH2.
20.
When 2-bromo-2-methylbutane undergoes an elimination reaction with hot alcoholic
KOH, two different alkenes can be formed. Deduce the names and formulas of these
two products.
21.
Show the E2 mechanism, using curly arrows, for the reaction between 2bromobutane and hot ethanolic NaOH.
p. 7