halo alkides

why are fluoralkanes unreactive

C-F bonds very strong, no reactions with the partial C+ bond

F very electronegative so the lone pairs are in very low energy orbitals

tertiary alkyl halides favour

SN1 reactions

primary and some secondary alkykl halides favour

SN2 reactions

SN2 reactions are backside attack

why are chloro, bromo, iodoalkanes reactive

Going from Cl to I, atomic radius gets bigger and there is a more poor overlapping of orbitals with the smaller C orbital. Electrons are very spaced out

Halide ions are quite strong and energetically favourable to form

Halide ions are good leaving groups

why don’t amines and alcohols undergo substitution

C-N and C-O bonds strong

an amide, NH2-, is terrible leaving group because N is not electronegative enough to stabilise the negative charge on the small ion

Hydroxide, OH-, is a bad leaving group because OH- isn’t stable enough to leave easily

elimination

only occur is Y- is a realatively strong base eg RO-- (alkoxide)

are the reverse of additions to alkenes

generally slower than substitution but can dominate if Y- is a large, strong, base