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Leaving Cert Chemistry: Organic synthesis

How often Organic synthesis comes up on the Chemistry papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 9 of the last 10 Ordinary Level papers, most recently in 2026. banker

June 2027 is the first exam on the new Chemistry course. These come from the 2016–2026 papers, so read them as a guide.

Organic synthesis, Higher Level(8 marks)

Quick ones on Organic synthesis.

(a)Test that shows both ethene and ethyne are unsaturated?
  1. They turn limewater milky
  2. They decolourise bromine water
  3. They relight a glowing splint
(b)Catalyst used in the school preparation of ethene from ethanol?
  1. Nickel
  2. Manganese dioxide
  3. Aluminium oxide
(c)Reagent used to convert a fat or oil into soap?
  1. Sodium hydroxide solution
  2. Bromine water
  3. Dilute hydrochloric acid
Show the answers

(a) They decolourise bromine water

(b) Aluminium oxide

(c) Sodium hydroxide solution

Your turn: Higher Level questions on Organic synthesis.

Higher Level

Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q2
2025Not asked
2024Q2
2023Q2
2022Q2
2021Q2, Q11(a)
2019Q2
2018Q2
2017Q2
2016Q8

Links open the State Examinations Commission’s paper for that year.

More Organic synthesis questions

Organic synthesis, 2 marks

Why is the mixture acidified at the end of the benzoic acid synthesis?

  1. To neutralise the benzoic acid so that it dissolves fully in the water
  2. To catalyse the oxidation of the starting material
  3. To turn soluble benzoate ions into benzoic acid, which crystallises
Show the answer

To turn soluble benzoate ions into benzoic acid, which crystallises

Under basic conditions the product is the soluble benzoate ion. Adding acid gives benzoic acid, which is only slightly soluble in cold water.

Organic synthesis, 2 marks

A surfactant such as soap works by?

  1. Killing all the bacteria on contact with the skin
  2. Lowering the surface tension of water so it can mix with grease
  3. Raising the surface tension of water so it holds grease
Show the answer

Lowering the surface tension of water so it can mix with grease

Each molecule has a non-polar tail that dissolves in grease and a charged head that stays in the water, so grease is lifted off.

Organic synthesis, 2 marks

Oxidising agent used in the school synthesis of benzoic acid from phenylmethanol?

  1. Potassium manganate(VII), basic
  2. Acidified sodium dichromate
  3. Fehling's solution
Show the answer

Potassium manganate(VII), basic

Phenylmethanol is refluxed with potassium manganate(VII) under basic conditions (with sodium carbonate). The mixture is acidified later.

Ordinary Level

Asked on 9 of the last 10 Ordinary Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q1
2025Q1
2024Q1
2023Q1, Q4(k)
2022Q1
2021Q1, Q4(k)
2019Q1
2018Q1
2017Not asked
2016Q1

Links open the State Examinations Commission’s paper for that year.

More Organic synthesis questions

Organic synthesis, 2 marks

Ethanol is made by fermenting sugar with?

  1. Aluminium oxide
  2. Sodium hydroxide
  3. Yeast
Show the answer

Yeast

Enzymes in yeast turn sugar into ethanol and carbon dioxide in the absence of air.

Organic synthesis, 2 marks

Soap is the sodium salt of a?

  1. Mineral acid (such as sulfuric acid)
  2. Fatty acid (long chain carboxylic acid)
  3. Long chain alcohol (fatty alcohol)
Show the answer

Fatty acid (long chain carboxylic acid)

The long hydrocarbon tail dissolves grease and the charged head dissolves in water.

Organic synthesis, 2 marks

How does ethyne burn in air?

  1. With a very smoky, sooty yellow flame
  2. With a clean blue flame and no smoke
  3. It does not burn at all
Show the answer

With a very smoky, sooty yellow flame

Ethyne has a high proportion of carbon, so it does not burn completely in air and gives off soot.

Other Chemistry topics

All of Leaving Cert Chemistry