How many \(\sigma \) and \(\pi \) bonds are present in a molecule of propyne, \({\text{C}}{{\text{H}}_{\text{3}}}{\text{CCH}}\)?

B

In this question candidates were asked to state the number of sigma and pi bonds in propyne. One respondent stated that as alkynes are not on the syllabus why the name was necessary. However, this question involved candidates drawing out the full structural formula using valency rules and hence counting the number of sigma and pi bonds. Knowledge of the alkyne functional group was not necessary but candidates did have to realise that a carbon to carbon triple bond was present. Often in questions the style of IB papers is to also include both the name and the associated structural formula.