Question

Conformations of Alkanes and Cycloalkanes 1) Draw a Newman projection of the anni conformation of 1.2-dichloroethane che conformation of 1.2-dichloroethane 2) Draw a Newman projection of the 5) Sight along the C2-C3 bond of 2-methylbutane and draw each of the staggered conformations 4) Arrange the following conformations from lowest to highest energy. CH CH 5) Circle the Most stable conformation of the molecule shown below. н сн, YI 6) Circle the Most stable conformation of the molecule shown below.

Answer 1

D Iz dichloroethane groups should In anti conformation, both 'cl be 180° apart from each other. (anti conformation) 2) In gauche conformation, two 'cl groups are separated by an angle of 60 Gauche form # #

13 Hz ~ &H - E - H3 atz d-methyl butane staggard conformations (two 'CH₂ groups are 180° apart) 4 CH3 - TH HE (all groups are apart) (CH₂-H eclipsing (CH₂ - CH₃ eclipse) lowest to highest energy eclipsing of CH₃ – CH3 groups gives more energy than Hz-Heclipsing.

v unstable, because stable, because - two gauche- - 2-CH3 groups are anti interactions of to each other CH3 groups - only one gauche-interaction of two ch₂ groups - because of steric repulsions, two bulky groups separated by 60° (gauche) will impart unstability) high energy for the conformation