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International A LevelChemistryEdexcelExam Questions4: Rates, Equilibria and Further Organic Chemistry4.8 Organic Chemistry: Carboxylic Acids

Organic Chemistry: Carboxylic Acids (Edexcel International A Level Chemistry)

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4.8 Organic Chemistry: Carboxylic Acids

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4.8 Organic Chemistry: Carboxylic Acids

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1a
Sme Calculator2 marks

This question is about an ester, Y, with the molecular formula C8H16O2.

Y contains 66.7% carbon, 11.1% hydrogen and 22.2% oxygen by mass. Show that these data are consistent with its molecular formula.

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1b3 marks

The structure of compound Y is

q17b-paper-4-2021-june-edexcel-ial-chemistry

i)
Give the IUPAC name of Y.
(2)

ii)
Draw the structures of two organic compounds that would react together to form Y.
(1)

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1c4 marks

The high resolution proton NMR spectrum of compound Y was obtained.

i)
Label the three remaining hydrogen environments B, C and D on the structure.

(1)

q17c-paper-4-2021-june-edexcel-ial-chemistry

ii)
Complete the table.
(3)
Hydrogen
environment		 Splitting pattern
of peak		 Relative
peak area
A triplet 3
B    
C    
D    

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1a3 marks

This question is about carboxylic acids and their derivatives.

Lactic acid, CH3CH(OH)COOH, is produced in muscles as a result of anaerobic respiration.

i)
The structure of lactic acid is

q17a-paper-4-jan-2021-edexcel-ial-chemistry

Give a reason why lactic acid shows optical isomerism.

(1)

ii)
A laboratory sample of lactic acid does not rotate the plane of plane-polarised monochromatic light.

Give a reason for this observation.

(1)

iii)
Give the structure of the organic product formed when lactic acid reacts with concentrated phosphoric(V) acid, H3PO4.

(1)

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1b3 marks

A reaction scheme involving butanoic acid is shown.

q17b-paper-4-jan-2021-edexcel-ial-chemistry

Identify X, Y and Z by name or formula.

Alcohol X
Reagent Y
Compound Z

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1c2 marks

The repeat unit of a polyester is shown.

q17c-paper-4-jan-2021-edexcel-ial-chemistry

Give the structures of the two monomers that could form this polyester.

Monomer 1

Monomer 2

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1d6 marks

An organic compound E contains carbon, hydrogen and oxygen only.

i)

The accurate relative atomic masses, Ar , of the three elements in E are shown in the table.

Element Ar
hydrogen 1.0078
carbon 12.0000
oxygen 15.9949

E contains five carbon atoms and gives a molecular ion peak at m / z = 102.0678 in its mass spectrum.

Deduce the molecular formula of E.

(1)

ii)
Aqueous sodium hydrogencarbonate is added to a sample of E.
No effervescence occurs.

State what can be deduced by this observation.
(1)
iii)
The infrared spectrum of E has an absorption in the range 1750 – 1735 cm−1.

Name the functional group in E.
(1)
iv)
Data from the high resolution proton NMR spectrum of E is shown.

Peak

Chemical shift, straight delta

/ ppm for TMS

 Splitting pattern Relative peak area
A 4.02 triplet 2
B 2.05 singlet 3
C 1.65 sextet 2
D 0.95 triplet 3

Deduce the structure of E.

Justify your answer by labelling the protons responsible for each peak.

(3)

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