whole of stereochemistry

what is isomerism

the existence of different compounds that have the same molecular formula

what are the two types of isomerism

• constitutional isomerism and stereoisomerism

two types of constitutional isomerism

ethanol and dimethyl ether

stereisomerism 3 main types

• conformational isomerism

• optical isomerism

• geometrical isomerism

what is conformational isomerism

differ by the rotation of covalent bonds giving different conformations of a compoundwha

what are the most significant conformers

eclipsed and staggered conformation

why is the staggered conformation the most stable conformer

the H atoms are as far apart as possible

what is the torsional energy

the energy required to rotate about the C-C bond

what is torsional strain

when we rotate away from the most stable conformation

with butane, what is the most stable conformation?

anti conformation , the max seperation of the two methyl gorups

what is the least stable structure

the eclipsed 1 structure - the 2 methyl groups that are closest together

what are cyclohexanes two main conformations

chair conformation and the boat conformation

what happens in the chair conformation

the H atoms are staggered and more stable

why is the boat conformation less stable

eclipsed H atoms

what is ring flipping

when one chair conformation can change to a second chair form via the boat conformation

why is ring flippinf important

when we have substituents attached to the cyclohexane ring

what is an equatorial atom

C-H bond in the plane of the ring

what is an axial atom

C-H bond vertical to the plane of the ring

what does ring flipping do to all equatorial bonds

converted to axial bonds and vice versa

why does bulky substituents preferentially occuoy the equatorial position

to minimise repulsion between atoms

what are configurational isomers

same molecular formula and connectivity but different orientation

what are optical isomers

configurational isomers that rotate plane polarized light

why is lactic acid non-superimposable

as it’s asymmetric

what is another name for an asymettric molecule

chiral molecule

what causes chirality in molecules

tetrahedral carbon atoms bonded to four diff atoms or groups

what is it called if a carbon has 2 or more identical atoms or groups

achiral

what is a chiral molecule and its mirror image called

enantiomer

what is an enantiomer

a structure that are not identical but are mirror images of each other

how are structures are chiral

if they cannot be superimposed on their mirror image

what is an equal mixture of enantiomers called

racemic

what is dextrorotatory

when the compound rotates the direction of plane polarised light in a clockrise direction

if the compound rotates the direction of plane polarised light in an anticlockwise direction what is it termed as

levorotatory

what is a diasteromer

when we have stereoisomers but not enantiomers