Characteristic Organic Reactions (Cambridge (CIE) AS Chemistry): Exam Questions

Alkenes are used as the starting point of many synthetic reaction pathways.

4-Methylpent-2-ene reacts with HBr to form 2-bromo-4-methylpentane as shown.

CH₃CH(CH₃)CHCHCH₃ + HBr → CH₃CH(CH₃)CH₂CHBrCH₃ 

Draw the mechanism of the reaction of 4-methylpent-2-ene with HBr.

• Draw the structure of 4-methylpent-2-ene and the intermediate.

• Include all charges, partial charges, lone pairs and curly arrows

State the role of HBr in the reaction in (a).

The halogenoalkane produced in (a) can be converted back into 4-methylpent-2-ene.

Identify the reagent(s) and conditions for this to occur.

Organic compounds can be grouped in homologous series.

i) Describe two characteristics of a homologous series. 

[2] 

ii) State the homologous series to which propene belongs. 

[1]

Propene can be converted into a mixture of 1-chloropropane and 2-chloropropane.

i) Identify a suitable reagent for this reaction. 

[1]

ii) Suggest which halogenoalkane formed in this reaction has a higher yield. Explain your answer. 

[1]

1-chloropropane and 2-chloropropane can be converted into compounds containing the nitrile functional group.

i) Identify a suitable reagent for the conversion of 1-chloropropane into butanenitrile, CH₃CH₂CH₂CN.

  [1]  

ii) 2-chloropropane can be converted into a structural isomer of butanenitrile. 

Name and draw the fully displayed formula of this isomer.

 [2]

A reaction scheme involving butanone is shown in Fig. 3.1.

Butanone  X Y 2-chlorobutane

Fig. 3.1

i) State suitable reagents for reactions 1 and 2. 

[2]

 ii) Deduce the type of reaction mechanism that occurs in reaction 2.  

[1]

Name and draw the mechanism for reaction 3 in Fig. 3.1.

Describe a chemical test and observation which would distinguish between butane and Y in Fig. 3.1.