Methanol (CH₃OH) is an important chemical in industry - Scottish Highers Chemistry - Question 8 - 2016

The structure for compound X is 2-methylpropene, which can be represented as:

     H   H
      \ /
       C
      / \
   H-C   C-H
      \ / 
       H

This structure allows for the addition reaction with methanol.

An atom economy of 100% means that all the atoms from the reactants are converted into the desired product without any waste. In this reaction, there are no by-products; therefore, every part of the reactants contributes directly to the formation of the target compound.

To calculate the enthalpy change:

1. Bond Breaking:

   • C-H bonds: 4 bonds x 412 kJ/mol = 1648 kJ
   • O-H bonds: 1 bond x 463 kJ/mol = 463 kJ
   • C-O bonds: 1 bond x 360 kJ/mol = 360 kJ
   • Total bond breaking = 1648 + 463 + 360 = 2471 kJ

2. Bond Formation:

   • C=O bonds: 1 bond x 743 kJ/mol = 743 kJ
   • H-H bonds: 2 bonds x 436 kJ/mol = 872 kJ
   • Total bond formation = 743 + 872 = 1615 kJ

3. Enthalpy Change:

   $ext{Enthalpy Change} = ext{Total bond breaking} - ext{Total bond formation} = 2471 - 1615 = 856 ext{ kJ/mol}$