Infrared (IR) spectroscopy can be used to identify functional groups in organic molecules. The IR spectrum of compound Y is shown.
(a) Identify the functional groups responsible for the absorptions around 3300 cm⁻¹ and 1710 cm⁻¹. [2] (b) Compound Y has the empirical formula C₂H₄O and a relative molecular mass of 88.1. Deduce the molecular formula of compound Y. [1] (c) Provide a textual description of a possible molecular structure for compound Y consistent with its empirical formula \(\mathrm{C_2H_4O}\), relative molecular mass of 88.1, and the IR absorption characteristics provided. Describe the connectivity, functional groups, and approximate arrangement using text and LaTeX for chemical formulas (for example, \(\mathrm{CH_3CH_2CH_2COOH}\)) without the need for a drawn structure. [1] (d) State one safety precaution necessary when handling unknown organic compounds in a laboratory. [1]
Part a
2 minutes
2 marks
Question
Identify the functional groups responsible for the absorptions around 3300 cm⁻¹ and 1710 cm⁻¹. [2]
Hint Hint
Hint
Check Data Booklet section on IR absorptions for O–H and C=O stretches.
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Complete Answer
O–H and C=O
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Part b
1 minutes
1 marks
Question
Compound Y has the empirical formula C₂H₄O and a relative molecular mass of 88.1. Deduce the molecular formula of compound Y. [1]
Hint Hint
Hint
Divide molar mass by empirical‐formula mass.
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C₄H₈O₂
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Part c
1 minutes
1 marks
Question
Provide a textual description of a possible molecular structure for compound Y consistent with its empirical formula \(\mathrm{C_2H_4O}\), relative molecular mass of 88.1, and the IR absorption characteristics provided. Describe the connectivity, functional groups, and approximate arrangement using text and LaTeX for chemical formulas (for example, \(\mathrm{CH_3CH_2CH_2COOH}\)) without the need for a drawn structure. [1]
Hint Hint
Hint
Include both the O–H and C=O groups in a C₄H₈O₂ skeleton.
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Complete Answer
Butanoic acid, which consists of a four‐carbon chain terminated by a carboxylic acid group (i.e., \(\mathrm{CH_3CH_2CH_2COOH}\)).
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Part d
1 minutes
1 marks
Question
State one safety precaution necessary when handling unknown organic compounds in a laboratory. [1]
Hint: The password should be at least eight characters long. To make it stronger, use upper and lower case letters, numbers, and symbols like ! " ? $ % ^ & ).
