Question

For each of the following compounds, predict the energy barrier to rotation (looking down any one of the C−C bonds). Draw a Newman projection and then compare the staggered and eclipsed conformations. Remember that we assigned 4 kJ/mol to each pair of eclipsing H’s and 6 kJ/mol to an H eclipsing a methyl group:

(a) 2,2-Dimethylpropane (b) 2-Methylpropane

explain it and show all the math please.

Answer 1

a) 2,2-dimethylpropane : CH₂-6 - CH3 Som CH3 B Srd99esed окса | mol Eclipsed Toral 3 eclipsing CHE/H i. 3 X 6 KJI Mol = 18 kJ/mol og OKJImol b) 2-methyl poop ane: GHạ– – Hạ CHE CH 4 X CH H H Staggoo ed O kJ/mol Eclipsed Two GHS/H eclipsing :: 276 kJ/mol = 12 kJ/mol + one HlH eclipsing IX 4 = 4 KlImol Total: 16 kJ/mol