Chapter 14: Alcohols (14.1-14.2)

Question 1

general formula of alcohols

Answer 1

Cn H2n+1 OH

Question 2

alcohol functional group

Answer 2

-OH (hydroxyl)

Question 3

polarity of alcohols

Answer 3

polar O-H bonds (oxygen is more electronegative than hydrogen)
therefore hydrogen bonds exist between molecules + there are polar bonds within the molecules

Question 4

melting and boiling points of alcohols

Answer 4

strong hydrogen bonds result in alcohols having relatively high melting/boiling points and low volatility (compared to alkanes of a similar mass)

Question 5

solubility of alcohols

Answer 5

Soluble in water (solubility decreases as the carbon chain length increases)
alcohols can from hydrogen bonds with water molecules, meaning alcohols with a SHORT carbon chain are soluble in water

Question 6

name the 3 types of alcohol

Answer 6

Primary (-OH group is bonded to a carbon atom that is only attached to 1 other carbon atom)
Secondary (-OH group attached to a carbon atom that is attached to 2 other carbon atoms)
Tertiary (-OH group attached to a carbon atom that it attached to 3 other carbon atoms)

Question 7

alcohol + oxygen –>

excess oxygen, complete combustion

Answer 7

CO2 (g) + H2O (l)

Question 8

oxidising agent for the oxidation of primary and secondary alcohols

Answer 8

acidified potassium dichromate(VI)
K2Cr2O7/H2SO4
represented as [O] in equation

Question 9

colour change of potassium dichromate to show oxidation of an alcohol

Answer 9

orange –> green

no colour change for tertiary alcohols as they cannot be oxidised

Question 10

oxidation of primary alcohols to aldehydes

Answer 10

primary alcohol is heated (with oxidising agent) under distillation
distilling off the aldehyde prevents furrier oxidation
aldehyde: RCHO

Question 11

oxidation of primary alcohols to carboxylic acids

Answer 11

primary alcohol is heated under reflux (w excess oxidising agent). Heating under reflux prevents the aldehyde, which initially forms from escaping so that full oxidation can take place and a carboxylic acid is formed.
carboxylic acid: RCOOH

Question 12

oxidation of secondary alcohols

Answer 12

secondary alcohol is heated under reflux (with oxidising agent) to form a ketone. Ketones cannot be oxidised further
ketone: RCOR

Question 13

elimination reactions of alcohols (dehydration)

Answer 13

dehydrating agents (e.g. H2SO4 or H3PO4) can be used to remove H2O from alcohols to from an alkene and water

Question 14

substitution reactions of alcohols

Answer 14

alcohols react with hydrogen-halides in acidic conditions to produce a haloalkane and water.
halide ion replaces OH group.