C14 Alcohols

Question 1

Functional group of alcohol

Answer 1

-OH (hydroxyl group)

Question 2

Physical properties of alcohols compared to alkanes

Answer 2

Less volatile

Higher MPs

Greater H2O solubility

Question 3

Reason for physical properties of alkanes

Answer 3

Non-polar bonds as EN of C + H very similar

IMFs between non-polar molecules are very weak LFs

Question 4

Reason for physical properties of alcohols

Answer 4

Polar O-H bonds (diff in EN of O and H atoms)

IMFs are very weak LFs but theres also strong HBs between polar O-H

Question 5

Why do alcohols have higher BPs and lower volatility than alkanes

Answer 5

HBs require more energy to break than weaker LFs in alkanes

Question 6

Solubility of alkanes in water

Answer 6

Non-polar

Cannot form HBs with H2O

Question 7

Solubility of alcohols in water

Answer 7

Completely soluble in water

HBs form between polar -OH groups of alcohol + H2O

Question 8

What happens to solubility as chain length increases

Answer 8

C chain length increases

Influence of -OH becomes smaller

Solubility decreases

Question 9

What’s a primary alcohol

Answer 9

-OH attached to C that’s attached to 2 H atoms + 1 alkyl group

Question 10

What’s a secondary alcohol

Answer 10

-OH attached to C that’s attached to 1 H + 2 alkyl groups

Question 11

What’s a tertiary alcohol

Answer 11

-OH attached to C that’s attached to no H + 3 alkyl groups

Question 12

What is the colour change when alcohols are oxidised

Answer 12

Orange to green

Dichromate (VI) ions reduced to chromium (III) ions

Question 13

What do primary alcohols oxidise to

Answer 13

Aldehyde or carboxylic acid

Question 14

Oxidation of primary alcohol to form aldehyde

Answer 14

Gentle heating

K2Cr2O7/H2SO4

Aldehyde distilled out as it forms

Colour change : orange to green

Question 15

Oxidation of primary alcohol to form carboxylic acid

Answer 15

Reflux

Excess K2Cr2O7/H2SO4

Orange to green

Form carboxylic acid + water

Question 16

What does oxidising secondary alcohols produce

Answer 16

Ketones

Question 17

Oxidising tertiary alcohols

Answer 17

Don’t undergo oxidation reactions

Oxidation mixture remains orange

Question 18

Oxidising secondary alcohol to produce ketone

Answer 18

Reflux

K2Cr2O7/H2SO4

Orange to green

Produce ketone + water

Question 19

Word equation of complete combustion of alcohol

Answer 19

Alcohol + O2 —> CO2 + H2O

Question 20

what is the oxidising agent that oxidises primary and secondary alcohols?

Answer 20

primary/secondary alcohol

heat under reflux

acid catalyst (conc H2SO4 or conc H3PO4)

form alkene and water

Question 21

what type of reaction is combustion?

Answer 21

exothermic reaction as it releases a large amount of energy in the form of heat.

Question 22

what conditions are needed for an alcohol to undergo a substitution reaction with a hydrogen halide?

Answer 22

hydrogen halide

reflux

sulfuric acid

sodium halide

forms haloalkane

Question 23

what is a dehydration reaction?

Answer 23

any reaction in which a water molecule is removed from the starting material