Acidic Environment 5

Question 1

differences between alkanols and alkanoic acid functional groups in C compounds.

Answer 1

Alkanols (R-OH) contain hydroxyl group (-OH) which gives their distinctive physical and chemical properties.
e.g methanol.
Polar -OH group makes alkanols polar with H bonding occurring between -OH groups.
Water soluble (although it decreases with increasing C chain length)
Higher mp and bp than corresponding alkanes/ alkenes.
React with alkanoic acids to form esters.

Alkanoic acids form homologous series of carbon compounds containing carboxyl group (-COOH) which gives distinctive physical and chemical properties.
E.g acetic acid.
Polar compounds due to presence of carboxyl group
From strong H bonds between nearby alkanoic acid molecules.
Water soluble due to H bonding (but decreases with icreasing C chain length)
Have higher mp and bp than corresponding alkanes, alkenes and alkanols
WA as they partly dissociate in water.

Question 2

IUPAC nomenclature for esters produced by reactions of straight chained alkanoic acids and straight chained primary alcohols.

Answer 2

• esters are organic compounds with general formula RCOOR’
  Formed from reacting alkanoic acids with alkanols.
  R and R’ represent C chain of varying lengths.
  E.g. Ethanol + butanoic acid ethyl butanoate + water
  When ethyl alcohol joins with butanoic acid, a water molecule (H-OH) is produced. The H- coming from the alchohol and the -OH from the acid. The remaining parts join to give the ester.

Question 3

Esterification

Answer 3

reaction between acid and an alkanol.
Alkanoic acid + alkanol ester + water.
E.g. Butanoic acid + ethanol ethyl butanoate + water
CONDENSATION REACTION as water is formed

Question 4

Acid is used during esterification for catalysis

Answer 4

• esterification is an equilibrium reaction that occurs slowly at room temp.
  Few drops of Conc. mineral acid (e.g. sulphuric acid) can be added as a catalyst to speed up reafction.
  Alkanoic acid + alkanol Ester + water

Question 5

Refluxing during esterification

Answer 5

is a way to preserve volatile components in the reaction mixture and stop them from evaporating. These volatile components cool in an upright condenser and flow back into reacting vessel.

Question 6

Examples of the occurrence, production and uses of esters

Answer 6

food (e.g. fats, fragrances and flavours)
Soaps (hydrolysing long chain esters founds in veg. oil and fats and as fragrances.)
medical uses ( e.g. nitroglycerine is used to dilate blood vessels)
Usually sweet smelling

Question 7

mp and bp of alkanols and alkanoic acids

Answer 7

Alkanols contain C-O and O-H bonds which are polar.
Strong intermolecular forces in alkanols. No alkanols are gases at room temp.
Higher bp for alkanoic acids than corresponding alkanols.
As chain length in alkanols and alkanoic acids increases, so do mp and bp but solubility in water decreases.

Question 8

Preparing an ester using reflux

Answer 8

OCTYL ETHANOATE (orange smelling)
50ml octan-1-ol and 50ml ethanoic acid in a flask
Add few drops of sulphuric acid, a few boiling chips and reflux.
CH3(CH2)6CH2OH + CH3COOH CH3COOCH2(CH2)6CH3 + H2O