DP Chemistry (first assessment 2025)
Question 19M.1A.HL.TZ2.36
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.1A.HL.TZ2.36 |
| Level | HL | Paper | 1A | Time zone | TZ2 |
| Command term | Question number | 36 | Adapted from | N/A |
36.
[Maximum mark: 1]
19M.1A.HL.TZ2.36
Which compound exists as two configurational isomers?
A. CBr2=CH2
B. CH2=CHBr
C. CHBr2CH2Br
D. CHBr=CHBr
[1]
Markscheme
D
Examiners report
71 % of the candidates identified 1,2-dibromoethene as having two configurational isomers. The most commonly chosen distractor was C which was the only saturated halogenoalkane, indicating that these candidates may have confused the term with “conformational” isomers.
Syllabus sections
Structure 3. Classification of matter » Structure 3.2—Functional groups: Classification of organic compounds » Structure 3.2.7—Stereoisomers have the same constitution (atom identities, connectivities and bond multiplicities) but different spatial arrangements of atoms. Describe and explain the features that give rise to cis-trans isomerism; recognize it in non-cyclic alkenes and C3 and C4 cycloalkanes. Draw stereochemical formulas showing the tetrahedral arrangement around a chiral carbon. Describe and explain a chiral carbon atom giving rise to stereoisomers with different optical properties. Recognize a pair of enantiomers as non-superimposable mirror images from 3D modelling (real or virtual).