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Organic chemistry
7 NET Chemistry questions with answers and explanations.
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What is the IUPAC name of (CH3)2CHCH3?
- 1 Butane
- 2 2-methylpropane
- 3 Propane
- 4 2-methylbutane
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Correct answer: 2-methylpropane
The longest chain has three carbons (propane) with a methyl group on carbon 2.
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Optical isomerism requires the presence of:
- 1 A double bond
- 2 A chiral carbon atom
- 3 A benzene ring
- 4 A hydroxyl group
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Correct answer: A chiral carbon atom
A carbon bonded to four different groups gives two mirror-image forms that rotate plane-polarised light in opposite directions.
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Which compound can undergo the aldol condensation?
- 1 Methanal
- 2 Ethanal
- 3 Benzaldehyde
- 4 2,2-dimethylpropanal
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Correct answer: Ethanal
Aldol condensation needs a hydrogen on the carbon next to the carbonyl group. Ethanal has one, and the others do not.
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Benzene reacts with bromine in the presence of FeBr3 to give:
- 1 Cyclohexane
- 2 Bromobenzene
- 3 Hexabromocyclohexane
- 4 Phenol
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Correct answer: Bromobenzene
This is electrophilic substitution. One hydrogen on the ring is replaced by bromine, and HBr is formed.
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How many sigma bonds are there in a benzene molecule?
- 1 9
- 2 6
- 3 12
- 4 15
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Correct answer: 12
There are six C-C sigma bonds and six C-H sigma bonds, so twelve in total.
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What is the functional group of an ester?
- 1 -COOH
- 2 -COO-
- 3 -CHO
- 4 -O-
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Correct answer: -COO-
An ester has the group -COO-, as in ethyl ethanoate, CH3COOC2H5.
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Which reagent converts a primary alcohol into a carboxylic acid on heating under reflux?
- 1 Acidified potassium dichromate
- 2 Concentrated sulphuric acid only
- 3 Sodium chloride
- 4 Dilute hydrochloric acid
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Correct answer: Acidified potassium dichromate
Acidified potassium dichromate is a strong oxidising agent that oxidises the alcohol, through the aldehyde, to the acid.