In the previous few posts, we discussed Newman projections, their use in illustrating and understanding the conformational analysis of open-chain and cyclic structures, such as chair conformations. This post is a summary of practice problems on Newman projections. … Read more
This comprehensive set of practice problems on Stereochemistry includes questions on determining R and S configuration, R and S configuration in Fischer and Newman projections, and determining the relationship between molecules such as enantiomers, diastereomers, and constitutional isomers. There are … Read more
Enantiomers and diastereomers are types of stereoisomers. Recall that stereoisomers are isomers with the same connectivity but different spatial arrangement of atoms. The isomers with different connectivity of atoms are called constitutional isomers: The (R)-2-chlorobutane and (S)-2-chlorobutane shown … Read more
We have learned that a Newman projection represents a molecule looking from a specified direction and a given bond. Therefore, a molecule can have multiple Newman projections depending on this bond and the direction we are looking from. For example, … Read more
Conformational analysis is the study of the relative stabilities of different conformations of a molecule. Recall that conformations or conformers are different spatial arrangements of atoms in the molecule, which are achieved as a result of rotations about single (σ) bonds. … Read more
Gauche conformation is a staggered conformation, and the name is associated with gauche interactions between methyl or other alkyl groups at a 60-dihedral angle. As a general representation, compare it with the anti conformation where the large groups are at 180o: … Read more
Newman Projections of Butane Let’s start today’s discussion with the definition of a conformation. The different spatial arrangements of the atoms that result from rotation about a single bond are called conformers or conformational isomers.To illustrate the conformations of butane, we need to … Read more
In the previous post, we talked about the staggered and eclipsed conformations of ethane, and saw that these are the least and most stable conformations that differ by a 12 kJ/mol rotation barrier: The staggered conformation is the … Read more
From General Chemistry and earlier chapters of Organic Chemistry, we know that C-C single bonds are formed by a linear overlap of sp3 orbitals. As an example, let’s recall how each carbon in ethane provides one sp3 orbital to form … Read more
Torsional and Steric Strain In the previous post, we talked about the Newman projections where we also covered the relative energies of anti, gauche, and syn conformations. The destabilization of certain conformations is due to Steric or Torsional strain. These two … Read more
