Topic 6 - Exam-style questions

Question 1

How many sigma and pi bonds are there in one molecule of cyclohexane

Answer 1

sigma bonds: 16
pi bonds: 1

Question 2

Which observation would be expected when 2-methylpropan-2-ol is heated with potassium dichromate and dilute sulfuric acid:
- orange to green
- green to orange
- purple to colourless
- no change

Answer 2

no change

Question 3

Which alcohol would be oxidised under reflux to produce this carboxylic acid:
- 1,1-dimethylethanol
- 2-methylpropan-1-ol
- 2-methylbutan-1-ol
- propan-2-ol

Answer 3

2-methylpropan-1-ol

Question 4

2-methylpropan-2-ol may be formed by the reaction between 2-bromo-2-methylpropane and aqueous potassium hydroxide.
What is the role of the hydroxide ion in this reaction:
- alkali
- catalyst
- electrophile
- nucleophile

Answer 4

nucleophile

Question 5

which of the following changes to the proportions of organic molecules within a fraction results from the reforming process:
- decrease/ increase in proportion of branched chain alkanes
- decrease/increase in proportion of cyclic hydrocarbons

Answer 5

• increase in proportion of branched chain alkanes
• increase in proportion of cyclic hydrocarbons

Question 6

The number of structural isomers with the molecular formula C5H12 is:
- 3
- 4
- 5
- 6

Answer 6

3

Question 7

what is the classification of the mechanism for the reaction between ethene and bromine:
- electrophilic addition
- electrophilic substitution
- nucleophilic addition
- nucleophilic substitution

Answer 7

electrophilic addition

Question 8

the heterolytic bond fission of a sigma bond in an alkane would produce:
- only carbocations
- only free radicals
- free radicals and ions
- ions

Answer 8

ions

Question 9

what is the classification of the mechanism for the hydrolysis of 2-chloro-2-methylpropane by water:
- addition
- elimination
- free radical substitution
- nucleophilic substitution

Answer 9

nucleophilic substitution

Question 10

which reagent is used with iodine to prepare iodoalkanes from alcohols:
- red phosphorus
- concentrated phosphoric acid
- sulfur
- concentrated sulfuric acid

Answer 10

red phosphorus

Question 11

Some alcohols react with concentrates phosphoric acid to form alkenes.
What is the type of this reaction?
- addition
- elimination
- oxidation
- substitution

Answer 11

elimination

Question 12

When butan-2-ol reacts with concentrates phosphoric acid, 2 stereoisomers are formed.
Explain what is meant by the term stereoisomers

Answer 12

have the sale structural formula, but the atoms have a different arrangement in the space

Question 13

Some alcohols can be oxidised by acidified sodium dichromate (VI), Na2Cr2O7.
Reflux apparatus can be used to carry out the oxidation of alcohols.
Using the apparatus for distillation instead of reflux is not an efficient way to produce ethanoic acid from ethanol. Explain why.

Answer 13

because ethanol would be oxidised into ethanal, because ethanal has a lower boiling point

Question 14

Primary alcohols react very slowly with concentrated hydrochloric acid.
State a different reagent for the chlorination of primary alcohols

Answer 14

PCl5 (Phosphorus (V) chloride)

Question 15

Reflux apparatus can be used to carry out the oxidation of alcohols.
State how the granules prevent bumping

Answer 15

the granules prevent uncontrolled boiling by distributing the heat evenly

Question 16

explain why the use of a reflux and a liebig condenser would give a very low yield of propanal

Answer 16

propanal is condensed back into the flask, so that it can be oxidised further into propanoic acid

Question 17

Ethanedioic acid can be prepare from ethane-1,2-diol. Give the reagent and condition required for this reaction

Answer 17

reagent: potassium dichromate
condition: heat under reflux