Which reagents are needed to convert nitrobenzene to phenylamine in 2 steps?

D

What is the number of optical isomers of isoleucine?

A. 0

B. 2

C. 4

D. 8

C

Which statement is correct for a pair of enantiomers under the same conditions?

A.  A racemic mixture of the enantiomers is optically active.

B.  They have the same chemical properties in all their reactions.

C.  They have the same melting and boiling points.

D.  They rotate the plane of plane-polarized light by different angles.

C

Which molecule is chiral?

A.     2-chlorobutane

B.     2,2-dichloropentane

C.     Propan-2-amine

D.     4-hydroxybutanoic acid

A

B

Which two molecules are cis-trans isomers of each other?

A.     X and Z

B.     X and Y

C.     W and Y

D.     W and Z

A

One respondent stated that this question was difficult. However, the question was in the midrange of difficulty and in fact was the \({\text{1}}{{\text{4}}^{{\text{th}}}}\) easiest question on the paper with 77.42% of candidates getting the correct answer, A. The question had a linked discrimination index of 0.40.

Which halogenoalkane reacts the fastest with hydroxide ions in a nucleophilic substitution reaction?

A.     1-chlorobutane

B.     2-chloro-2-methylpropane

C.     1-iodobutane

D.     2-iodo-2-methylpropane

D

Which molecule exhibits optical isomerism?

A.     3-iodopentane

B.     2-iodo-2-methylpropane

C.     1,3-diiodopropane

D.     2-iodobutane

D

Propene is reacted first with hydrogen chloride to produce X which is then reacted with aqueous sodium hydroxide to give Y. Finally, Y is reacted with excess acidified potassium dichromate solution.

\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{CHC}}{{\text{H}}_{\text{2}}}\xrightarrow{{{\text{HCL}}}}{\text{X}}\xrightarrow{{{\text{NaOH(aq)}}}}{\text{Y}}\xrightarrow{{{{\text{H}}^ + }/{\text{C}}{{\text{r}}_2}{{\text{O}}_7}^{2 - }{\text{(aq)}}}}{\text{Z}}\]

What is the major product, Z? 

A.     CH₃CH(OH)CH₃

B.     CH₃COCH₃

C.     CH₃CH₂CHO

D.     CH₃(CH₂)₂COOH

B

Which molecule has a chiral centre?

A.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{CH=CHCHO}}\)

B.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{2}}}{\text{C=CHC}}{{\text{H}}_{\text{2}}}{\text{OH}}\)

C.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{OC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}\)

D.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{CHOHC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}\)

D

In this question, candidates had to identify which molecule had a chiral centre. One respondent stated that ethers are off-syllabus. It is true that as a functional group, ethers are not required based on Topic 10. However, it should be noted that candidates are expected to know that oxygen is divalent and hence can occur with two single bonds. This is also referred to in the Teacher’s notes corresponding to AS 4.3.2, where a comparison between the intermolecular forces present in \({\text{C}}{{\text{H}}_{\text{3}}}{\text{OC}}{{\text{H}}_{\text{3}}}\) and \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{OH}}\) is referred to. Hence, candidates are expected to be able to write a full structural formula from the condensed structural formula of \({\text{C}}{{\text{H}}_{\text{3}}}{\text{OC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}\) to determine that it does not have a chiral centre.

A

What is name of this compound applying IUPAC rules?

A.     E 1-bromo-1-chlorobut-1-ene

B.     Z 1-bromo-1-chlorobut-1-ene

C.     E 1-bromo-1-chloro-2-ethylethene

D.     Z 1-bromo-1-chloro-2-ethylethene

B

Which statements about substitution reactions are correct?

I.     The reaction between sodium hydroxide and 1-chloropentane predominantly follows an \({{\text{S}}_{\text{N}}}{\text{2}}\) mechanism.

II.     The reaction between sodium hydroxide and 2-chloro-2-methylbutane predominantly follows an \({{\text{S}}_{\text{N}}}{\text{2}}\) mechanism.

III.     The reaction of sodium hydroxide with 1-chloropentane occurs at a slower rate than with 1-bromopentane.

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

B

Which compound can exist as stereoisomers?

A.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CHO}}\)

B.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{COC}}{{\text{H}}_{\text{3}}}\)

C.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{CH(C}}{{\text{H}}_{\text{3}}}{{\text{)}}_{\text{2}}}\)

D.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CHOHC}}{{\text{H}}_{\text{3}}}\)

D

Which isomers exist as non-superimposable mirror images?

A.     cis-trans isomers

B.     diastereomers

C.     enantiomers

D.     structural isomers

C

Which molecule exhibits optical isomerism?

A.     3-chloropentane

B.     2-chlorobutane

C.     1,3-dichloropropane

D.     2-chloro-2-methylpropane

B

Which type(s) of stereoisomerism, if any, is/are present in the molecule CH₂=CHCHBrCH₃?

A.     Optical only

B.     Geometric only

C.     Optical and geometric

D.     Neither optical nor geometric

A

Nearly a quarter of the candidates were persuaded, presumably by the C=C, to chose option C.

Which factors affect the rate of nucleophilic substitution in halogenoalkanes?

I.     The nature of the attacking nucleophile

II.     The identity of the halogen

III.     The structure of the halogenoalkane

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

D

What does a polarimeter measure?

A.     Colour of reaction mixture

B.     Polarity of a molecule

C.     Configuration of a molecule as R or S

D.     Rotation of plane-polarized light

D

The examiners regret the inclusion of R and S in the distractors. In the event, this question was the fifth easiest with over 84% giving the correct answer.

Which reaction occurs via a free-radical mechanism?

A.     \({{\text{C}}_2}{{\text{H}}_6} + {\text{B}}{{\text{r}}_2} \to {{\text{C}}_2}{{\text{H}}_5}{\text{Br}} + {\text{HBr}}\)

B.     \({{\text{C}}_2}{{\text{H}}_4} + {\text{B}}{{\text{r}}_2} \to {{\text{C}}_2}{{\text{H}}_4}{\text{B}}{{\text{r}}_2}\)

C.     \({{\text{C}}_4}{{\text{H}}_9}{\text{I}} + {\text{O}}{{\text{H}}^ - } \to {{\text{C}}_4}{{\text{H}}_9}{\text{OH}} + {{\text{I}}^ - }\)

D.     \({{\text{(C}}{{\text{H}}_3})_3}{\text{CI}} + {{\text{H}}_2}{\text{O}} \to {{\text{(C}}{{\text{H}}_3}{\text{)}}_3}{\text{COH}} + {\text{HI}}\)

A

Halogenoalkanes can undergo \({{\text{S}}_{\text{N}}}{\text{1}}\) and \({{\text{S}}_{\text{N}}}{\text{2}}\) reactions with aqueous sodium hydroxide. Which halogenoalkane will react fastest with a \({\text{0.1 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) solution of aqueous sodium hydroxide?

A.     2-chloro-2-methylpropane

B.     2-iodo-2-methylpropane

C.     1-chlorobutane

D.     1-iodobutane

B

What is the product of the reaction between pentan-2-one and sodium borohydride, NaBH₄?

A. Pentan-1-ol

B. Pentan-2-ol

C. Pentanoic acid

D. Pentanal

B

Which compound could rotate the plane of polarization of polarized light?

A.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{2}}}{\text{CHC}}{{\text{H}}_{\text{2}}}{\text{Cl}}\)

B.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{Cl}}\)

C.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CHClC}}{{\text{H}}_{\text{3}}}\)

D.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CCl}}\)

C

What is the major organic product formed from the reaction of (CH\(_3\))\(_3\)CBr with a concentrated, ethanolic solution of KOH?

A.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{COH}}\)

B.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{2}}}{\text{CC}}{{\text{H}}_{\text{2}}}\)

C.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{2}}}{\text{CO}}\)

D.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{2}}}{\text{CHO}}\)

B

Which halogenoalkane reacts fastest with sodium hydroxide?

A.     1-iodobutane

B.     1-chlorobutane

C.     2-chloro-2-methylpropane

D.     2-iodo-2-methylpropane

D

1-bromobutane, \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{Br}}\), can be converted to 1-aminopentane, \({\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{N}}{{\text{H}}_{\text{2}}}\), in a two-step process.

\[\begin{array}{*{20}{l}} {{\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{Br}}\xrightarrow{I}{\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{CN}}} \\ {{\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{CN}}\xrightarrow{{II}}{\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{C}}{{\text{H}}_2}{\text{N}}{{\text{H}}_2}} \end{array}\]

What are the reagents I and II?

D

Which molecule contains a chiral carbon?

A.     CH₃CH₂CHBrCH₂CH₃

B.     CH₃CH₂CHBrCH₃

C.     CH₂BrCH(CH₃)CH₂Br

D.     CH₃CH₂CH₂CH₂CH₂Br

B

How many four-membered ring isomers are there of dichlorocyclobutane, \({{\text{C}}_{\text{4}}}{{\text{H}}_{\text{6}}}{\text{C}}{{\text{l}}_{\text{2}}}\)?

A.     3

B.     4

C.     5

D.     6

C

This question tested assessment statement 20.6.3. The question was poorly answered with 30% choosing A and 41% B. It was the most difficult question in the paper answered correctly by only 17%.

What should be changed to alter the rate of nucleophilic substitution of tertiary halogenoalkanes?

A.     The nucleophile

B.     The concentration of the nucleophile

C.     The concentration of the tertiary halogenoalkane

D.     The size of the reaction flask

C

Students found this question one of the more difficult ones with 32.32% correct answers. Tertiary halogenoalkanes undergo SN1 reaction mechanism in which the rate of reaction is only first order with to the concentration of the halogenoalkane; thus choice C was the correct answer.

Which pair of isomers always shows optical activity?

A.     Cis-trans

B.     Enantiomers

C.     Conformational

D.     E/Z

B

Which compound is optically active?

B

Several respondents suggested that it would have been better if atomic labels were given in the 3D diagrams in this question which is a fair comment.

Which compound can exist as stereoisomers?

A.     1,2-dichloroethane

B.     1,1-dichloroethene

C.     Butan-2-ol

D.     Propan-2-ol

C

One can only apologise for the error in distractor B; it will be corrected in the published version.

Which statement is correct about the enantiomers of a chiral compound?

A.     Their physical properties are different.

B.     All their chemical reactions are identical.

C.     A racemic mixture will rotate the plane of polarized light.

D.     They will rotate the plane of polarized light in opposite directions.

D

One respondent stated that there were two answers to this question (A and D). The only correct answer is D, namely that, the enantiomers of a chiral compound rotate the plane of polarized light in opposite directions. Enantiomers have the same physical properties. However, diastereomers which are stereoisomers that are not enantiomers can have different physical properties.

Which compound has a chiral carbon?

A.     Propan-2-ol

B.     1-bromo-2-methylbutane

C.     3-bromopentane

D.     Ethane-1,2-diol

B

What is the correct order for the increasing rate of hydrolysis of halogenoalkanes by dilute aqueous sodium hydroxide?

A.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{CH(C}}{{\text{H}}_{\text{3}}}{\text{)C}}{{\text{H}}_{\text{2}}}{\text{Cl}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{CHClC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}} < {{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CCl}} < {{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CBr}}\)

B.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CBr}} < {{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CCl}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{CHClC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{CH(C}}{{\text{H}}_{\text{3}}}{\text{)C}}{{\text{H}}_{\text{2}}}{\text{Cl}}\)

C.     \({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CCl}} < {{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CBr}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{CHClC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{CH(C}}{{\text{H}}_{\text{3}}}{\text{)C}}{{\text{H}}_{\text{2}}}{\text{Cl}}\)

D.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{CHClC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}} < {\text{C}}{{\text{H}}_{\text{3}}}{\text{CH(C}}{{\text{H}}_{\text{3}}}{\text{)C}}{{\text{H}}_{\text{2}}}{\text{Cl}} < {{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CBr}} < {{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CCl}}\)

A

What is the name of the following compound applying IUPAC rules?

A.     cis-4-methylhex-2-ene

B.     cis-4-ethylpent-2-ene

C.     trans-4-methylhex-2-ene

D.     trans-4-ethylpent-2-ene

C

The hydrolysis of tertiary bromoalkanes with a warm dilute aqueous sodium hydroxide solution proceeds by a two-step \({{\text{S}}_{\text{N}}}{\text{1}}\) mechanism.

     Step I:     \({\text{R}} - {\text{Br}} \to {{\text{R}}^ + }{\text{B}}{{\text{r}}^ - }\)

     Step II:     \({{\text{R}}^ + } + {\text{O}}{{\text{H}}^ - } \to {\text{R}} - {\text{OH}}\)

Which description of this reaction is consistent with the above information?

B

What is the product of the reduction of 2-methylbutanal?

A.     2-methylbutan-1-ol

B.     2-methylbutan-2-ol

C.     3-methylbutan-2-one

D.     2-methylbutanoic acid

A

Which is the correct combination of substitution reaction mechanisms?

A

Which structure is a geometric isomer of cis-1,2-dichlorocyclobutane?

A

This was the second most difficult question on the paper, the most popular answer being D. Candidates have clearly misread the question.

In which order should the reagents be used to convert benzene into phenylamine (aniline)?

C

Which statement about isomerism is correct?

A.     But-1-ene and but-2-ene are geometrical isomers.

B.     But-1-ene has two geometrical isomers.

C.     Butan-1-ol and butan-2-ol are optical isomers.

D.     Butan-2-ol has two optical isomers.

D

What effect of optical isomers on plane-polarized light can be measured using a polarimeter?

A.     Reflection

B.     Emission

C.     Rotation

D.     Absorption

C

Propanitrile can be prepared by reacting bromoethane with potassium cyanide. Which statement is not correct about the reaction between bromoethane and potassium cyanide?

A.     The reaction is bi-molecular.

B.     The reaction follows the \({{\text{S}}_{\text{N}}}{\text{2}}\) mechanism.

C.     Homolytic fission occurs between the carbon-bromine bond in bromoethane.

D.     The cyanide ion, \({\text{:C}}{{\text{N}}^ - }\), acts as a nucleophile.

C

One respondent stated that propanenitrile should have been written instead of propanitrile, which is correct.

A

Which pair are geometric isomers?

D

Propene reacts separately with H₂O/H⁺ and H₂/Ni to give products X and Z respectively. 

What are the major products of the reactions?

A

Which statement about stereoisomers is correct?

A. 1,2-dichloroethane has two geometrical isomers.

B. 1,2-dichloroethane has two optical isomers.

C. 1,2-dichloroethene has two geometrical isomers.

D. 1,2-dichloroethene has two optical isomers.

C

Which is correct for the conversion of propanal to propyl methanoate?

D