stereochemistry

What are Isomers?

Molecules that have an identical molecular formula, but differ in some structural way (e.g., in atom connections or spatial orientation).

What are the two main categories of Isomerism?

structural Isomerism and Stereoisomerism.

Define Structural (Constitutional) Isomers

Molecules that have the same molecular formula, but different arrangements of the atoms in the molecule (the compounds differ in the order the atoms are connected).

List the types of Structural Isomerism.

Carbon chain isomerism, Positional isomerism, Functional group isomerism, Tautomerism.

Define Stereoisomers.

Molecules that have both the same molecular formula and structural formula (atoms connected in the same way), but differ in the spatial arrangement of the atoms in the molecule.

What are the two main types of Stereoisomerism?

Diastereomers and Enantiomers. (Also includes E/Z Isomerism and R/S Isomerism as sub-types or methods of distinction).

Define Enantiomers.

isomers that are mirror images of each other

What is the key difference between two enantiomers?

The 3D arrangement of the four groups around the asymmetric carbon atom.

What are the physical properties of enantiomers?

Identical physical properties (e.g., boiling point, melting point, density) except for their rotation of plane-polarized light.

Define Diastereomers.

stereoisomers that are not mirror images

What are the physical properties of diastereomers?

Diastereomers have different physical properties melting points, boiling points, densities, solubilities, refractive indices, dielectric constants and specific rotations.

How are diastereomers typically separated?

separate by techniques such as distillation, recrystallization, and chromatography, due to their different physical properties.

What is one class of diastereomers?

Cis-trans isomers (also known as geometric isomers).

Do cis-trans isomers have a mirror image relationship?

No, they are not mirror images of each other; therefore, they are not enantiomers.

What is the maximum number of stereoisomers for a molecule with 'n' stereogenic (chiral) centers?

2^n

How is the carbon chain typically drawn in a Fischer projection?

: Along the vertical line of the projection, with the most highly oxidized carbon substituent at the top.

how do you draw a mirror image of a Fischer projection?

Simply exchange the groups on the left and right positions, while keeping the top and bottom unchanged

What is the utility of Fischer projections in determining chirality?

useful for determining if a compound is chiral or achiral.

In a Fischer projection, if the mirror image cannot be made to look like the original image by only rotating by 180° in the plane of the paper, what does this indicate?

The images are enantiomers, and the original compound is therefore chiral.

Are mirror planes of symmetry easy to identify in Fischer projections?

yes

If a molecule drawn as a Fischer projection has a mirror plane of symmetry, can it be chiral?

No, molecules with mirror planes of symmetry cannot be chiral.