Organic chemistry

Alkenes contain a carbon-carbon double bond consisting of a high electron density pi bond, which readily attracts electron-deficient electrophiles. They do not contain 'free electrons' as seen in metallic bonding, nor are the carbons naturally positively charged before the reaction starts.

The SN2 mechanism is a single-step bimolecular reaction where the nucleophile attacks from the backside, leading to a transition state and stereochemical inversion. A carbocation intermediate is incorrect because that species is characteristic of the two-step SN1 mechanism instead.

Alkanes are saturated hydrocarbons containing only single covalent C-C and C-H bonds, meaning they contain the maximum possible number of hydrogen atoms per carbon. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

• !Option A is incorrect because molecules containing carbon-carbon double bonds are classified as unsaturated alkenes.
• !They do not contain 'free electrons' as seen in metallic bonding, nor are the carbons naturally positively charged before the reaction starts.
• !Ketones are incorrect because they are formed from the oxidation of secondary alcohols, not primary ones.
• !A carbocation intermediate is incorrect because that species is characteristic of the two-step SN1 mechanism instead.

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