Alcohols and Esters: Chemistry 9701 (Cambridge International AS & A Level)

A student warms a sample of 2-methylbutan-2-ol under reflux with an excess of acidified potassium dichromate(VI) solution for 20 minutes.

Which observation is correct?

3-Methylbutan-1-ol, $(\text{CH}_3)_2\text{CHCH}_2\text{CH}_2\text{OH}$, is a colourless liquid with a strong odour, used industrially as a solvent.

(a) State whether 3-methylbutan-1-ol is a primary, secondary or tertiary alcohol. Explain your answer by referring to the number of carbon groups attached to the carbon bearing the $-\text{OH}$ group. [1]

(b) 3-Methylbutan-1-ol is heated under reflux with an excess of acidified potassium dichromate(VI) for an extended period, so that oxidation goes to completion. Give the name and structural formula of the organic product formed, and describe the colour change of the dichromate(VI) solution. [3]

(c) Describe how the experimental technique would need to be changed so that the aldehyde is obtained as the major product instead, starting from the same alcohol and the same oxidising agent. [2]

(d) 3-Methylbutan-1-ol is warmed with concentrated hydrobromic acid. Name the type of mechanism involved, and give the structural formula of the halogenoalkane formed. [2]

Propyl ethanoate, $\text{CH}_3\text{COOCH}_2\text{CH}_2\text{CH}_3$ ($M_r = 102$), can be made from propan-1-ol and ethanoic acid, and can also be hydrolysed back to its starting materials.

(a) Write an equation, using structural formulas, for the formation of propyl ethanoate from propan-1-ol and ethanoic acid, and name this type of reaction. [3]

(b) State the role of the concentrated sulfuric acid used in this reaction. [1]

(c) A $5.10\ \text{g}$ sample of propyl ethanoate is refluxed with an excess of aqueous sodium hydroxide until hydrolysis is complete. Calculate the maximum mass of sodium ethanoate, $\text{CH}_3\text{COONa}$ ($M_r = 82$), formed. [3]

(d) Explain, in terms of the position of equilibrium, why hydrolysis of propyl ethanoate with aqueous sodium hydroxide goes to completion, whereas hydrolysis with dilute aqueous acid does not. [2]

Ethyl benzoate can be prepared by two different routes.

Route 1: benzoic acid is heated under reflux with ethanol, using concentrated sulfuric acid as a catalyst.

Route 2: ethanol is added dropwise, at room temperature, to benzoyl chloride.

Which statement correctly compares these two routes?

A few drops of acidified potassium dichromate(VI) solution are added to a warmed sample of butan-2-ol, $\text{CH}_3\text{CH(OH)CH}_2\text{CH}_3$.

Which statement correctly describes what is observed and what organic product is formed?

Pentan-1-ol, $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}$, can be dehydrated to form an alkene.

(a) State two different sets of conditions that could each be used to dehydrate pentan-1-ol to an alkene. [2]

(b) Name the type of reaction occurring, and write an equation, using structural formulas, for the dehydration of pentan-1-ol. [3]

(c) Explain why pentan-1-ol yields only a single alkene product on dehydration, whereas dehydrating pentan-2-ol can yield a mixture of two structurally isomeric alkenes. [2]

Propan-1-ol, $\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}$, is used as a fuel.

(a) Write a balanced equation, using whole-number coefficients, for the complete combustion of propan-1-ol in an excess of oxygen. [2]

(b) State the difference in the oxygen supply between complete and incomplete combustion, and give the formula of one product (other than water) formed during incomplete combustion of propan-1-ol. [2]

(c) Explain, in terms of the carbon and oxygen content of the fuel molecule, why alcohols such as propan-1-ol generally burn with a less smoky flame than a hydrocarbon of a similar chain length, such as propane. [2]

Methyl propanoate, $\text{CH}_3\text{CH}_2\text{COOCH}_3$, can be hydrolysed under acidic or alkaline conditions.

(a) Name the alcohol and the carboxylic acid from which methyl propanoate could be formed by esterification. [2]

(b) Write an equation, using structural formulas, for the acid hydrolysis of methyl propanoate using dilute sulfuric acid under reflux, and state whether this reaction goes to completion. [3]

(c) Write an equation, using structural formulas, for the alkaline hydrolysis of methyl propanoate using aqueous sodium hydroxide, and name the two organic products formed. [3]

Solid phosphorus(V) chloride is added to a small, dry sample of ethanol, $\text{CH}_3\text{CH}_2\text{OH}$.

Which statement correctly describes the observation and the organic product formed?

2-Methylpropan-1-ol, $(\text{CH}_3)_2\text{CHCH}_2\text{OH}$, can undergo the three separate reactions described below.

Reaction 1: 2-methylpropan-1-ol is heated under reflux with an excess of acidified potassium manganate(VII).

Reaction 2: 2-methylpropan-1-ol vapour is passed over a heated aluminium oxide catalyst.

Reaction 3: 2-methylpropan-1-ol is heated under reflux with ethanoic acid and a few drops of concentrated sulfuric acid.

(a) For Reaction 1, give the structural formula of the organic product and state the colour change observed. [3]

(b) For Reaction 2, name the type of reaction and give the structural formula of the alkene formed. [3]

(c) For Reaction 3, name the type of reaction and give the structural formula of the ester formed. [3]