Knights content L1-5
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What is the name given to isomers which DIFFERENT connectivity
Constitutional isomers
What is the name given to isomers with the same connectivity
Stereoisomers
What is the name of isomers which interconvert by rotation
Conformational isomers
What is the name of isomers which do not interconvert by rotation
Configurational isomers
What two groups do stereoisomers divide into
Configurational and conformational Isomers
What is the name give to isomers that do not interconvert by rotation but are not mirror images
Diasteroisomers
What is the name given to isomers that do not interconvert by rotation but are mirror images
Enantiomers
What are the two groups within Configurational isomers
Diasteroisomers and enantiomers
When is a molecule chiral
A molecule is chiral if it has a non superimposable mirror image
What are enantiomers
The two mirror image forms of a molecule
What do enantiomers possess
Enantiomers have identical melting and boiling points, nmr spectra and IR spectra
When would enantiomers not have identical physical and chemical properties
When placed in a chiral environment ie when interacting with other chiral, non racemic molecules
Describe enantiomers in the presents of plane polarised light
When a beam of plane-polarized light is passed through a chiral compound the plane of the polarization is rotated through an angle. One enantiomer will rotate the plane clockwise and the other enantiomer will rotate the light anticlockwise by the same amount
What does the size of angle rotated by the enatiomer in plane polarised light depend on
Path length, solvent concentration, temperature and wavelength
What is the observed angle of rotation denoted by and what do we call this
Denoted by [a] a is alpha This is also known as as specific rotation
What is the equation to calculate specific rotation and what do the letters stand for
[a] = a/c.l x100 a is observed rotation C is concentration in g per 100ml l is path length in decimetres
What is the D/L nomenclature used for
The D/L nomenclature is nowadays only used for certain classes of compound, such as carbohydrates and amino acids.
How do we assign D or L to molecules
In order to assign a molecule as D or L, we simply need to compare the configuration to that of glyceraldehyde
What configuration are all of the naturally occurring amino acids and which is the exception
All of the naturally occurring amino acids are L except glycine which is achiral
Define enatiomerically pure
If a sample of a chiral compound consists of a single enantiomer it can be referred to as enatiomerically pure
Define racemic
An equal mix of enantiomers is a racemic mixture
Define scalemic
If the mixture of enatiomers is not 50:50 then it is called scalemic
How to we report the enantiomeric purity of a compound
The enantiomeric purity of a compound reported by quoting the enantiomeric excess (ee)
How do we calculate the enantiomeric excess
ee = (moles of one enantiomers) - (moles of another enantiomer) / total number of moles X 100