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Basic concepts of organic chemistry

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Question 3

Selenols are organic compounds containing the −SeH-\text{SeH}−SeH (selenium-hydrogen) functional group, which are the selenium analogues of alcohols and thiols.

a.

Ethaneselenol (C2H5SeH\text{C}_2\text{H}_5\text{SeH}C2​H5​SeH) behaves as a weak acid in aqueous solution. Write the expression for the acid dissociation constant, KaK_{\text{a}}Ka​, for ethaneselenol.

[1]
b.

Selenols react with carboxylic acids in a condensation reaction to form selenoesters. Write a balanced chemical equation for the reaction between ethaneselenol and butanoic acid (CH3CH2CH2COOH\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}CH3​CH2​CH2​COOH). Use structures for all organic compounds with their functional groups clearly displayed.

[2]
c.

Draw the skeletal formula for 4-methylpent-4-ene-1-selenol.

[1]
d.

Propane-1,3-diselenol (HSeCH2CH2CH2SeH\text{HSeCH}_2\text{CH}_2\text{CH}_2\text{SeH}HSeCH2​CH2​CH2​SeH) reacts with carbonyl compounds to form a cyclic selenoacetal in a condensation reaction. Write a balanced chemical equation for the reaction of propane-1,3-diselenol with propanone (CH3COCH3\text{CH}_3\text{COCH}_3CH3​COCH3​). Use structures for all organic compounds.

[2]
Markscheme

Basic concepts of organic chemistry Questions

  1. A Level
  2. /Chemistry
  3. /Basic concepts of organic chemistry

18 exam-style questions on OCR A A Level Chemistry Basic concepts of organic chemistry. Each one has a worked solution and a mark scheme showing where the marks go.

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