DP Chemistry Questionbank

Describe what happens to plane-polarized light when it passes through a solution of an optically active compound.

Vision is dependent on retinol (vitamin A) present in retina cells. Retinol is oxidized to the photosensitive chemical 11-cis-retinal and isomerizes to 11-trans-retinal on absorption of light.

Outline how the formation of 11-trans-retinal results in the generation of nerve signals to the brain.

A mixture of enantiomers shows optical rotation.

Suggest a conclusion you can draw from this data.

Below are two isomers, A and B, with the molecular formula C₄H₉Br.

Explain the mechanism of the nucleophilic substitution reaction with NaOH(aq) for the isomer that reacts almost exclusively by an S_N2 mechanism using curly arrows to represent the movement of electron pairs.

Which molecule has an enantiomer?

A.  ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{CH}\left(\mathrm{OH}\right){\mathrm{CH}}_2{\mathrm{CH}}_3$

B.  ${\mathrm{CH}}_2\left(\mathrm{OH}\right){\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}={\mathrm{CH}}_2$

C.  ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{CH}=\mathrm{CHBr}$

D.  ${\mathrm{CH}}_3{\mathrm{CHBrCH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_3$

Which compound rotates the plane of plane-polarized light?

A.  CH₃C(CH₃)ClCH₃

B.  CH₃CH₂CHClCH₃

C.  CH₃C(Cl)₂CH₃

D.  CH₃CClBrCH₃

Which molecule contains a chiral carbon?

A.     CH₃CH₂CHBrCH₂CH₃

B.     CH₃CH₂CHBrCH₃

C.     CH₂BrCH(CH₃)CH₂Br

D.     CH₃CH₂CH₂CH₂CH₂Br

Suggest, giving a reason, the percentage of each isomer from the S_N1 reaction.

Sketch the wedge and dash (3-D) representations of alanine enantiomers.

How many chiral carbon atoms are present in one molecule of (CH₃)₂CHCHClCHBrCH₃?

A.   0

B.   1

C.   2

D.   3

Identify the isomer of Compound B that exists as optical isomers (enantiomers).

Draw the full structural formula of (Z)-but-2-ene.

The organic product is not optically active. Discuss whether or not the organic product is a racemic mixture.

Outline why the major product, C₆H₅–CHBr–CH₃, can exist in two forms and state the relationship between these forms.

Two forms: 

Relationship:

The minor product, C₆H₅–CH₂–CH₂Br, can exist in different conformational forms (isomers).

Outline what this means.

Label with an asterisk, *, the chiral carbon atom.

Which can show optical activity?

A.  CHBrCHCl

B.  CH₃CH₂CHBrCH₂CH₃

C.  (CH₃)₂CBrCl

D.  CH₃CH₂CH(CH₃)Br