Organic Chemisty Part 3

Question 1

What are alcohols?

Answer 1

-OH functional group
Suffix -ol
General formula Cn H2n+2 O
Very flammable
Unsaturated (all single bonds)

Question 2

Combustion of ethanol in air (complete combustion)

Answer 2

Cobalt chloride paper blue -> pink
Limewater colourless -> cloudy

Ethanol + oxygen -> carbon dioxide + water
C2H6O + 3O2 -> 2CO2 + 3H2O

Question 3

Reaction of ethanol with oxygen in air

Answer 3

Produces vinegar (aqueous solution of ethanoic acid)
Microbial action
Oxidation reaction

Ethanol + oxygen -> ethanoic acid + water
C2H6O + O2 -> CH3COOH + H2O

Question 4

Reaction when heating acidified potassium dichromate (VI) in ethanol

Answer 4

Potassium dichromate solution orange -> green
Smells like vinegar

Dichromate (vi) ion (orange) reduced to chromium (iii) ion (green)
Ethanol oxidised

Question 5

How can ethanol be manufactured?

Answer 5

Hydration of ethene OR fermentation of glucose

Question 6

Hydration of ethene to produce ethanol

Answer 6

C2H4 + H2O -> C2H5OH
Use phosphoric (v) acid as catalyst
Optimum conditions are 300°C and 60-70atm
Efficient as uses continuous flow process, very rapid
Produces very pure ethanol
Uses high temperatures and pressures, needs lots of energy input (crude oil)
Expensive as lots of equipment needed

Question 7

Fermentation of glucose to produce ethanol

Answer 7

C6H12O6 -> 2C2H5OH + 2CO2
Needs sugar in water, yeast as catalyst temperature of 30-40°C, absence of acid
After a few days, process stops as high alc content (up to 14%) kills of yeast
Produces impure ethanol
Slow/inefficient batch process
Gentle temperature and pressure, little energy needed

Question 8

What are carboxylic acids?

Answer 8

Functional group COOH
General formula CnH2nO2
Carbon-carbon double bond
Suffix -oic + acid
Eg ethanoic acid (vinegar)
Weak acids

Question 9

Reaction of carboxylic acids with metals

Answer 9

carboxylic acid + metal -> salt + hydrogen
eg ethanoic acid + sodium -> sodium ethanoate + hydrogen
Test for gas produced using squeaky pop test

Question 10

Reaction of carboxylic acid with metal carbonates

Answer 10

Carboxylic acid + metal carbonate -> salt + water + carbon dioxide

eg ethanoic acid + sodium carbonate -> sodium ethanoate + water + carbon dioxide
eg CH3COOH + Na2CO3 -> 2NaCH3COO + H2O + CO2

Effervescence

Question 11

What are esters?

Answer 11

Functional group COO
Made by reacting an alcohol with a carboxylic acid with sulphuric acid catalyst (condensation polymerisation)
eg ethyl ethanoate (C4H8O2) is ethanol + ethanoic acid
Alcohol prefix +yl, ethanoic acid prefix +oate
Strong fruity smells
Can be used as solvents

Question 12

What is a polymer?

Answer 12

Lots of small molecules joined up

Question 13

Positives and negatives of polymers

Answer 13

They can be strong, flexible and durable

They are hard to dispose of as they are inert and non-biodegradable

Biopolysters are biodegradable

Question 14

Disposal of polymers by incineration

Answer 14

The heat produced can be used as an energy source

Carbon dioxide and other toxic gases are produced, contributing to global warming

Question 15

Disposal of polymers by recycling

Answer 15

Reduces the amount of crude oil used, no toxic gases produced

Requires sorting, melting and reforming polymers can be expensive and difficult

Question 16

Condensation polymerisation

Answer 16

Reaction between monomers with functional groups at both ends, produces polymer and water molecule
eg polyester
dicarboxylic acid + diol -> polyester + water