Organic | Introduction to organic chemistry

Question 1

Draw the E and Z forms of a structural isomer of C5H10O that shows both optical and geometric isomerism.

Answer 1

E
OH
H CHCH3
C=C
CH3 H

Z
OH
CH3 CHCH3
C=C
H H

Question 1

This question is about isomers with the molecular formula C5H10O
(a) Draw the skeletal formula of a branched chain aldehyde with molecular
formula C5H10O that is optically active.

Answer 1

• 4 carbon chain
• O branches off (double bond)
• methyl group on carbon-3

Question 2

Which compound has E–Z isomers?
A CH2=CHBr
B CH2=CBr2
C CHBr=CHBr
D CBr2=CHBr

Answer 2

C

Question 3

Which is the correct general formula for non-cyclic compounds in the homologous series?
A alcohols CnH2n+2O
B aldehydes CnH2n+1O
C esters CnH2n+1O2
D primary amines CnH2n+2N

Answer 3

A = alcohols

Question 4

Explain the differences between structural isomerism and stereoisomerism. Use examples to show how compounds with the molecular formula C4H8 exhibit stereoisomerism and the three types of structural isomerism. (6)

Answer 4

1a. Structural isomers: same molecular formula but different structural formula
1b. Stereoisomers: molecules with same molecular formula but different arrangement of atoms in space.

STEREOISOMERS
2a. lack of rotation around C=C
2b. Structures of E and Z of but-2-ene
2c. correct identity of E and Z isomers.

STRUCTURAL ISOMERS
3a. different carbon chain e.g: methylpropene & but-1-ene.
3b. different position of functional groups e.g. but-1-ene and but-2-ene.
3c. different functional group e.g: cyclobutane and but-1-ene