CHEM 212 Lecture Notes - Lecture 3: Bromine, Margarine, Trans Fat
Document Summary
Chem 212: introductory organic chemistry 1 lecture 3: alkanes and cycloalkanes-- Conformations--molecular shapes that result from -bond rotation. Staggered conformation is favoured over eclipsed conformation because of 2 reasons. Hyperconjugation--electron delocalization through orbital overlap between a filled. Minimum steric repulsion staggered lower energy more stable eclipsed higher energy less stable. Ethane mainly exists in staggered form, but conformers interconvert rapidly. Syn conformation unfavoured because of vander waal"s repulsion. Anti conformation is favoured because of two reasons: Hyperconjugation-electron delocalization through orbital overlap between a filled. Butane has two staggered forms (anti > gauche), still interconverts rapidly. Butane has larger torsional barrier than ethane because butane"s steric hindrance is greater than that of ethane. Very important: all alkane chains prefer anti--ch3(ch2)nch3 zig zag . Unlike the alkanes, cycloalkanes have limited rotation about c-c bonds, which leads to more rigid structures. Cyclopropane: angle strain + torsional strain = highest ring strain.