Alkenes

Question 1

What are the criteria for cis-trans isomerism?

Answer 1

Covalent bond with restricted rotation (e.g. double bonds or rings)
Different groups attached to each carbon atom on each end of the restricted bond.

Alkenes may exhibit cis-trans isomerism if the above criteria are met.

Question 2

Describe what is Saytzeff’s rule and a brief reason for it (the mechanism not in syllabus but need to know reason)

Answer 2

Saytzeff’s rule is for the elimination of alcohols to form alkenes. Saytzeff’s rule states that the C=C bond is formed such that the major product formed is the most highly substituted alkene.

Reason: greater number of alkyl groups, more stable.

Question 3

State the conditions for the dehydration/elimination of alcohols to form alkenes

Answer 3

1. Excess conc h2so4, heat
   2 conc h3po4, heat
2. Alumina, heat

Question 4

State the conditions for dehydration/elimination of haloalkane (RX) to form alkenes

Answer 4

Ethanolic KOH, HEAT UNDER REFLUX