Organic Chemistry Answers

1. Show the structural formulae for the main product of each of the following

addition reactions between various

e) 2-Methylbut-2-ene and hydrogen iodide

f) But-1-ene and hydrogen bromide where everything is pure

g) but-1-ene and hydrogen bromide in the presence of oxygen or

organic peroxides and a hydrogen halide.

In functional group, how can you distinguish between hexylamine (C6H13NH2) and aniline? Like, is there a type of test that should be used to differentiate them ?

Reaction of 2-methyl-1,3-butadiene with bromine yields a mixture of products: 3,4-

dibromo-2-methyl-1-butene (3 %), 3,4-dibromo-3-methyl-1-butene (21 %) and 1,4-

dibromo-2-methyl-2-butene (76 %).

a) Identify all products as either 1,2 or 1,4 adducts. (3)

b) Propose mechanisms for the formation of all 3 products. (9)

c) Explain why 3,4-dibromo-3-methyl-1-butene (21 %) predominates over 3,4-dibromo-2-

methyl-1-butene (3 %).

Calculate the rate constant k from the gradient of the graph, drawn for part (c). All calculations must be shown

Plot a ‘rate against concentration of OH^-‘graph from your results in part (b). Label the vertical and horizontal axes of the graph and include the units. The graph MUST be hand-drawn or plotted by hand.

1-Bromobutane was hydrolysed by an aqueous sodium hydroxide (NaOH) solution. 

     CH₃CH₂CH₂CH₂Br    +   NaOH     →      CH₃CH₂CH₂CH₂OH      +     NaCl 

        1-Bromobutane                                             Butan-1-ol

                       During the reaction, the reactant sodium hydroxide is used up. Samples of the reaction mixture were drawn off at regular time intervals and analysed by titration with standard sulfuric acid to find out the concentration of sodium hydroxide. 

      The results are given in the table below:

 Time / s Concentration of OH-  / mol dm-3

0 0.500

100 0.350

200 0.250

300 0.180

400 0.125

500 0.090

600 0.063

700 0.040

800 0.030

 Select 4 suitable points along your graph [see part (a)] and draw tangents to find the rates. Construct a table of “Rate” against “Concentration” (2 marks). The rates need to be calculated and the calculations shown 

Use electronic and stability factors to account for the acidity of each hydrogen in

the m-hydroxybenzoic acid. Identify the most acidic proton.

a) How does the rate of the reaction change as you go along the series HF – HCl

– HBr – HI?

b) Briefly explain the trend you have given in part (a).

c) How does the rate of reaction change as you go from ethene to propene to 2-

methylbut-2-ene?

1. Show the structural formulae for the main product of each of the following

addition reactions between various alkenes and a hydrogen halide.

a) Ethene and hydrogen bromide

b) But-2-ene and hydrogen chloride

c) But-1-ene and hydrogen chloride

d) Propene and hydrogen iodide

e) 2-Methylbut-2-ene and hydrogen iodide

f) But-1-ene and hydrogen bromide where everything is pure

g) but-1-ene and hydrogen bromide in the presence of oxygen or

organic peroxides

1. Show the structural formulae for the main product of each of the following

addition reactions between various alkenes and a hydrogen halide.

a) Ethene and hydrogen bromide