(6) Isomerism Flashcards
what is isomerism and two types
same molecular but different arrangement of atoms; structural and stereoisomerism
what is structural isomerism and the three types
atoms bonded in a different order; functional group, positional and chain isomerism
what is functional group isomerism
same molecular formula but atoms are arranged to change functional group
what is positional isomerism
same molecular formula and functional group. Functional group has moved to a different position on carbon chain.
what is chain isomerism
same molecular formula but different arrangement of carbon skeleton
what is stereoisomerism and the two types
atoms bonded in the same order but arranged differently in space, geometric and optical isomerism
what is geometric isomerism
restricted rotation (often involving C=C) and two different groups on the left hand of the bond and two different groups on the right hand of the bond
what is optical isomerism
two compounds that contain the same connectivity and different spacial arrangements of the atoms but have non-superimposable mirror images EG: lactic acid
ketone
.O
II
R-C-R
aldehyde
.O
II
R-C-H
carboxylic acid
.O
II
R-C-OH
what are two optical isomers called
enantiomers
what does optically active mean
substances that can rotate the plane of the plane-polarised light
what is plane-polarised light
light that has been passed through a polarising filter. The waves all travel in the same plane so the plane can be rotated from left to right (due to spatial arrangement of the atoms)
what are the types of optical isomers
d-isomer (rotates plane to the right) and I-isomer (rotates plane to the left)
what is a chiral (asymmetric chiral centre)
an atom with 4 different atoms or groups of atoms attached to it. (identified using *)
what is achrial
a molecule without a chiral centre and it is optically inactive (cannot rotate plane)
what is chirality
one of the isomers is non-superimposable mirror image of the other
what is a racemic mixture
a mixture of optical isomers which contain equal numbers of moles of each of the d-isomers and i-isomers; there is no overall effect on the plane rotation
what is stereospecificity due to
the stereospecific nature of the receptor sites to which the drugs bind
how are receptor sites stereospecific
due to the functional groups that are present in the site. they can only interact with one of the optical isomers bc of the position of the groups/ isomer may not fit into the active site
why would racemic mixtures such as isoflurane not be separated
there are no harmful/ unwanted effects from the other optical isomer and would be more expensive to separate them
