Organic Chemistry II: Chirality (Edexcel A Level Chemistry): Flashcards

A chiral centre is a carbon atom bonded to four different atoms or groups of atoms, giving the molecule a handedness with no plane of symmetry.

False.

A racemic mixture is optically inactive. One enantiomer rotates plane-polarised light clockwise and the other rotates it anticlockwise by the same amount, so the effects cancel out and there is no net rotation.

Enantiomers are non-superimposable mirror images of each other. They are the two optical isomers of a molecule containing one chiral centre.

In an S_N1 reaction, the intermediate carbocation is trigonal planar, so the nucleophile can attack from either side, producing a racemic mixture.

Optical isomers are pairs of molecules that are non-superimposable mirror images, arising from the presence of a chiral centre in the molecule.

An S_N2 reaction starting from an enantiopure chiral halogenoalkane produces an enantiopure product with an inverted configuration. The nucleophile can only attack from the opposite side to the leaving group, causing the molecule to turn inside out like an umbrella.

Plane-polarised light is light in which the waves vibrate in one plane only, produced by passing unpolarised light through a polariser.

Two enantiomers have different biological effects because they interact differently with biological receptors, which are themselves chiral. The receptor recognises only one specific spatial arrangement, so each enantiomer produces a different response — for example, the two enantiomers of carvone smell of spearmint and caraway respectively.

A racemic mixture (or racemate) is a mixture containing equal amounts of each enantiomer, making it optically inactive because the rotations cancel out.