R-ATCHE-24

Production of esters:

• Carboxylic acid + alcohol $\rightleftharpoons$ ester

Note! Both forward and reverse reactions tend to use a $H_{2}SO_{4}$ catalyst to occur, since both occur at normal conditions, but at very slow rates!

Notice how the resultant ester has the alcohol first, then the carboxylic acid, for the carbon lengths.

• I.e. suppose we reacted ethanoic acid with methanol. The product would be methyl ethanoate.
• You can think about this at the carboxylic acid becoming an "oate" ion, i.e. it loses the $H$ from the $OH$ section of the $COOH$ group.

This kind of reaction is called condensation

Properties

• Polar, due to the double bonded oxygen, and reasonably polar C-O single bond.
  • Cannot form hydrogen bonds with itself, but can form hydrogen bonds with water, i.e. molecules with hydrogen (bonded to NOF).
• As it cannot form hydrogen bonds with itself, it has a low M.P/B.P. But it can form H bonds with water, hence it is reasonably soluble.
  • Less soluble than alcohols, carboxylic acids, since their hydrogen bonding capacity is decreased, but since they can form some/half of a hydrogen bond they are more soluble than for example propane.

Reversible reaction

• Warm the ester with $H_{2}SO_{4}$ the reverse reaction will occur.
• This is called hydrolysis!

• Warm with $OH^{-}$ (e.g. $NaOH$) gives alcohol back and carboxylic acid salt ion!
  • i.e. we have neutralised the acid, we have the resultant "oate" ion.
• e.g. $CH_{3}COOH$ + $OH^{-}$ $\to$ $CH_{3}OH$ + $CH_{3}COO^{-}$

Observations

• Two layers form (generally)
  • Due to limited solubility of ester in water (though as before more soluble than your usual non-polar stuff)
• Sweet smelling odour.

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