Stereochemistry (U2,c3/6) Flashcards
What are isomers?
Compounds that have the same molecular formula but differ in structural formulae
What are geometric isomers?
Stereoisomers where there is a lack of rotation around one of the bonds, mostly a C=C
What is a cis geometric isomer?
One in which both groups are on the same side of the C=C bond
What is a trans geometric isomer?
One in which both groups are on the opposite sides of the C=C bond
What are optical isomers?
Non-superimposable mirror images of asymmetric molecules - Chiral molecules or enantionmers
What can be said about physical or chemical properties of isomers?
They can be very different.
Where is optical isomerism immensely important?
Biological systems
What is a racemic mixture?
A mixture of equimolar optical isomers (which is optically inactive)
What effect does a racemic mixture have on the rotation of plane polarised light?
No effect - The rotational effect of one isomer is cancelled out by the opposite rotational effect of the other.
What is true of structural isomers in terms of atom arrangement?
Their atoms are bonded together in a different order.
What is true of stereoisomers in terms of atom arrangement?
The atoms are bonded in the same order, but the arrangement of the atoms in space is different for each isomer.
What are the two kinds of stereoisomers?
Geometric and optical isomers.
What kind of molecules can be geometric isomers?
Molecules with a C=C bond, and also saturated rings where rotation around the C-C bond is restricted.
What do chiral compounds NOT have?
A centre/plane/axis of symmetry.
Optical isomers are identical in all physical properties except… what?
Their effect on plane polarised light, i.e. they exhibit optical activity.
