PH1125- chemistry Flashcards
what is an electrophile ?
An electrophile is an atom or molecule that accepts an electron pair to make a covalent bond.
what is a Brønsted Lowry acid ?
A substance that donates a proton (H+)
what is a Brønsted Lowry base ?
A substance that accepts a proton (H+)
what is the general “leaving group ability” order ? (best to worst)
+NMe3 > TsO- > I- > Br- > -OH2+ > Cl- > F- > OH-
what is a Lewis base
An electron pair donor
what are nucleophiles? (2)
- ‘love nuclei’ which means they wish to form bonds by donating or sharing their electrons
- they are electron rich and are usually negative ions or neutral molecules with electron lone pairs
what is a leaving group? (2)
- a stable species that detaches itself from a molecule with its electron pair during the course of a reaction
- they are usually expelled with a negative charge and form very stable chemical species after the reaction
What happens to nucleophilicity as you go across the periodic table ?
- increases from right to left
- increases as you go down
what is an SN2 reaction? (2)
- one bond is broken and one bond is formed synchronously i.e. in one step
- substitution, nucleophilic, bimolecular
what does bimolecular mean?
- both the nucleophile and electrophile are involved in the reaction
what does the rate of SN2 depend on? (4)
- structure of the electrophile
- primary carbon; fast
- secondary carbon; slow
- tertiary carbon; impossible
how to tertiary haloalkanes react?
- SN1
what is an SN1 reaction? (2)
- two step process where only one species is involved in the slow step
- substitution, nucleophilic, unimolecular
what does the rate of SN1 depend on? (4)
- the more stable the carbocation, the faster the reaction
- tertiary carbon; fast
- secondary carbon; intermediate
- primary carbon; impossible
why do e1 elimination reactions work best for tertiary alcohols?
- more stable carbocations
