Alcohols and Carbonyls

Ethanol. Alkanol family, Aldehydes and Ketones. Methanol and Methanal

Index

Ethanol

Homologous series CnH2n+1OH

Alcohol structures

Oxidation of alcohols

Aldehydes and Ketones

Methanol

Ethanol C2H5OH

CC H

H

H

H OH

HFunctional group -OH

Hydrogen bonding allows ethanol to dissolvein water, pH 7. b.p. 78 oC.This effect decreases in alcohols as the length of the hydrocarbon chain increases. Hydroxyl group

CH3CH2OH + 3 O2 2 CO 2 + 3 H2O H = - 1367 kJ mol -1

Combustion of ethanol

Ethanol is a good solvent, it behaves both like water and other hydrocarbon solvents.

Ethanol can be used as a fuel in cars.

H

HH

OR O -+

+

-

+

Ethanol C2H5OHManufacture of Ethanol

Fermentation is used to make all alcohol based drinks.Any vegetable matter containing carbohydrates can be used.

2. Hydration of Ethene (Industrial manufacture of Ethanol)

1. Fermentation

C2H4 + H2O CH3CH2OH

yeast

Cracking fractions from crude oil is a cheaper way to produce ethanol.(more expensive than making petrol)

C6H12O6 2CH3CH2OH + 2CO 2

Reaction Conditions:300oC , High Pressure 60 Atm. , phosphoric acid catalyst.

Uses of EthanolDrinks Ethanol is a natural product of fermentation.

Ethanol cannot be more than 15% of the fermentation mixture, as ethanol is a poison and will kill the yeast.

Solvent In varnishes (as it evaporates easily), dyes, perfumes anddrugs.

Chemical feedstock

In the production of vinegar, ether, chloroform and ethyl esters and ethene.

Increasingly seen as an important fuel. Meths is ethanolwith added methanol. Cars can use ethanol as a fuel.

Fuel

Others In thermometers (cheaper and safer than Hg and de-icers.

Dehydration of ethanol

CH3CH2OH C2H4 + H2O

Ethanol Ethene

Catalyst

When hot ethanol is passed over aluminium oxideethene gas is produced.

Ethene is very a very important chemical, it is the basisfor many plastics. E.g. Polythene

Homologous Series CnH2n+1OH

Methanol, CH3OH; Ethanol C2H5OH; Propanol C3H7OH

Functional molecular structure

Propanol C3H7OH, has 2 isomers, propan-1-ol and propan-2-ol.

Straight chain isomers of Alkanols

propan-1-ol

propan-2-ol

CC C

H

H

H

H

H

H

OH

H

CC C

H

H

H

H

OH

H

H

H

1. Decide on the type of compound (ie. consider functional group)

2. Select the longest chain

3. Name the compound with the branched chains in ascending order.

alcohol (alkanol)

4 C’s butanol

2-methylbutan-1-ol

H

H

C

H

H

C

H

H

H

C

OH

H

CH3

CNaming alcohols

Different types of alcohol

Primary alcohol, 1 C joined to theC bonded to the OH group

Secondary alcohol, 2 C’s joined to theC bonded to the OH group

Tertiary alcohol, 3 C’s joined to theC bonded to the OH group

2-methylpropan-2-olpropan-2-ol

CC H

H

H

H OH

H

C O

C

H

C

CH O

C

H

C

C

CH3C

CH3

CH3

OH

CC C

H

H

H OH

H

H H

H

Other Alcohols1. Cycloalkanol

Cyclohexanol is a secondary alcohol

2. Diols (dihydric)

Ethane-1,2-diolAnti freeze

3. Triols (Trihydric)e.g. propane –1,2,3,triol or Glycerol is used in cosmetics, paints andnitroglycerine explosives.

C

C

C

C

C

C

H

H

H OH

H

H

H

H HH

H

H

CC

OH

H

H H

H

OH

Oxidation of Alcohols

Primary alcohols can be oxidised in two stages, 1st Stage - Hydrogen is lost; 2nd Stage - oxygen is gained.

Secondary alcohols can be oxidised to form ketones, Tertiary alcohols do not undergo oxidation.

C=O carbonyl group

C

O H

H

H

+ OR C H

O

R

oxidation

H2O+

aldehyde

OO+C H

O

R

aldehyde

C H

O

R

acid

oxidation

R C R1

O

ketone

1st

2nd

Aldehydes and Ketones

Methanal, 40% in water is formalin, and is used to make polymers

Propanone, nail varnish remover and is used in the making of perspex

Ethanal, It’s trimer (CH3CHO)3 is used as a sleep inducing drug. It also causes a hangover

Butanone, is a solvent used to make VHS tapes.

CHO alkanal functional group C=O ketone functional group

H

HC = O

-+

CH3

HC = O

CH3CH2

CH3

C = O

Butan-2-one C4H8O

CH3

CH3

C = O

Aldehydes and Ketones(Using mild oxidising agents.)Distinguishing tests

Aldehydes are oxidised to carboxylic acids

1. Fehlings solution contains Cu2+ ions (blue) which form Cu+ ion (orange-red) in the presence of aldehydes.

2. Tollen’s reagent contains Ag+ ions, which form Ag in the presenceof aldehydes (silver mirror test)

Ketones do not react with oxidising agents.

3. Acidified Potassium Dichromate orange Cr2O72-(aq) to green

Cr3(aq)

RSC video on silver mirror

Methanol, Steam reformingThe steam used must be pure.

Methanol is oxidised into methanal, either by:

1. Zinc/Chromium oxide catalysts 350-450oC and 200-300 Atm.2. Cu/Zn/Al oxide catalysts 175-300oC and 40-100 Atm.

CH3OH + O2 HCHO + H20

Carbon + steam Carbon monoxide + hydrogen

1. Coal 1000 oC synthesis gas

Methane + steam Carbon monoxide + hydrogen

2. Natural Gas (UK)900 oCNi Catalyst30 Atmos

synthesis gas

Uses for Methanol and Methanal

FuelAdded to ethanol to make meths, cleaner flame than hydrocarbons.

Added to petrol octane number 114. MTBE (Methyl Tertiary Butyl Ester)

Can be converted into petrol using Zeolite.

Drugs and Fabrics

Formalin, preserve biological specimens

PolymersPolymethanal, machine parts

Melamine, Electrical insulators

Phenol methanal, heat resistant are all thermosettings plastics

Methanol Methanal