Topic 3.3.1: Introduction to Organic Chemistry Exam Practice

(a)

• Compounds with the same molecular formula but different structural formulae. [1]

(b) Any two of the following pairs:

• 1-chlorobutane: CH3CH2CH2CH2Cl [1]
• 2-chlorobutane: CH3CH2CH(Cl)CH3 [1]
• OR: 1-chloro-2-methylpropane ( (CH3)2CHCH2Cl ) and 2-chloro-2-methylpropane ( (CH3)3CCl ).

(a)

• Both molecules have restricted rotation around the carbon-carbon double bond (C=C). [1]
• In but-2-ene, each carbon of the double bond is attached to two different groups (a methyl group and a hydrogen atom). In propene, one of the double-bonded carbons is attached to two identical hydrogen atoms. [1]

(b)

• Identify the two groups attached to each C atom of the double bond. Assign priority to each group based on the atomic number of the atom directly attached to the C (highest atomic number has the highest priority). [1]
• If the two highest priority groups are on the same side of the double bond, it is the Z-isomer (Zusammen). If they are on opposite sides, it is the E-isomer (Entgegen). [1]

(a)

• Homolytic fission: Covalent bond breaks and one electron from the shared pair goes to each of the bonding atoms, forming two free radicals. [1]
• Heterolytic fission: Covalent bond breaks and both electrons from the shared pair go to only one of the bonding atoms, forming a cation and an anion. [1]

(b)

• A curly arrow represents the movement/transfer of electrons. [1]
• A double-headed arrow represents the movement of an electron pair, whereas a single-headed (fishhook) arrow represents the movement of a single electron. [1]