Eduqas A-Level Chemistry A410QS
Formulae and Equations
Basic Ideas About Atoms
Chemical Calculations
Bonding
Solid Structures
The Periodic Table
Simple Equilibria and Acid-Base Reactions
Thermochemistry
Rates of Reaction
The Wider Impact of Chemistry
Organic Compounds
Hydrocarbons
Halogenoalkanes
Alcohols and Carboxylic Acids
Instrumental Analysis
Redox and Standard Electrode Potential
Redox Reactions
Chemistry of the P-Block
Chemistry of the D-Block Transition Metals
Chemical Kinetics
Enthalpy Changes for Solids and Solutions
Entropy and Feasibility of Reactions
Equilibrium Constants
Acid-Base Equilibria
Stereoisomerism
Aromaticity
Alcohols and Phenols
Aldehydes and Ketones
Carboxylic Acids and Their Derivatives
Amines
Amino Acids, Peptides and Proteins
Organic Synthesis and Analysis
Specified Practical Work
Practical Skills and Techniques
Mathematical Skills in Chemistry
Organic Synthesis and Analysis
Combining spectra to elucidate a structure
- 3 things to know
- Component 2
Overview
Recall questions on identifying compounds from a combination of mass, infrared and NMR evidence, which technique gives the molecular formula, which the functional groups and which the skeleton, worked identifications, and why one technique alone is rarely enough.
What you need to know
Answer each one before you reveal it.
A compound of formula C₃H₆O gives one singlet in its proton NMR. What is it?
How would propanal be distinguished from propanone by proton NMR?
Questions from this subtopic
Each one with the model answer underneath.
- 1
A compound of relative molecular mass 60 shows a broad infrared absorption from 2500 to 3200 cm⁻¹ and a strong peak at 1710 cm⁻¹. What is it?
Model answer
Ethanoic acid, since that pair of absorptions is the carboxylic acid O—H and C=O and the formula CH₃COOH has a relative molecular mass of 60.
- 2
Confirm that identification from the proton NMR.
Model answer
Ethanoic acid gives two singlets in the ratio 3 : 1, the methyl near 2.1 and the acid hydrogen far downfield beyond 10 parts per million.
- 3
A compound of formula C₃H₆O gives one singlet in its proton NMR. What is it?
Model answer
Propanone, whose six hydrogen atoms are all equivalent.
- 4
How would propanal be distinguished from propanone by proton NMR?
Model answer
Propanal gives three peaks including one near 9.7 parts per million from the aldehyde hydrogen, while propanone gives a single peak.
- 5
How would propanal be distinguished from propanone by infrared alone?
Model answer
Propanal shows a weak C—H absorption near 2750 to 2850 cm⁻¹ from the aldehyde group, which propanone does not.
- 6
How would propanal be distinguished from propanone by a chemical test?
Model answer
Propanal reduces Tollens' reagent to give a silver mirror and reduces Fehling's solution to a red precipitate, while propanone does neither.
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