Consider the compound \({\text{(C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{)CH=CH(C}}{{\text{H}}_{\text{3}}}{\text{)}}\). Which statements are correct?

I.     A suitable name is pent-2-ene.

II.     The empirical formula is \({\text{C}}{{\text{H}}_{\text{2}}}\).

III.     An isomer of the compound is pentane.

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

A

Three respondents commented on this question. One respondent stated that a 3D structure should not be used here. As previously mentioned in this report, candidates should be encouraged to see a whole range of different representations of structures and in organic chemistry it is especially important that candidates are exposed to 3D representations as part of the overall teaching of organic chemistry. Another respondent stated that it would have been better if statement I. was instead given as a suitable name for the compound is pent-2-ene, which is a fair comment. This was mirrored by another respondent who stated that the molecule drawn is in fact a geometrical isomer and hence E should have been used. Although this is correct, at SL in Topic 10, it is clearly stated that the distinction between cis and trans isomers is not required (TN for AS 10.1.8), so this is the reason why reference was not given to (2E)-pent-2-ene in the question, so the respondent is correct in stating that it would be better if the term IUPAC name was not given for this reason.