Alkyl Halide Sn1 Reactions Flashcards
Sn1 Reaction Outline
Rate determining step is dependent on 1 molecule. The strength of the leaving group (the nucleophile plays no part at all in the rate determining step). Reaction takes 2 steps
What alkyl halides undergo Sn1 Reactions
tertiary and some secondary (the more complex the substituents the less likely a Sn2 reaction occurs)
Nucleophile Outline
Substance (charged or neutral) with a lone pair of electrons
What charge does the intermediate in a Sn1 reaction have if the nucleophile is negatively charged
Neutral
What charge does the intermediate in a Sn1 reaction have if the nucleophile is neutral
positive. Has to lose a proton in the next step
What influences the strength of a nucleophile
How alkaline it is. The stronger the base = the more likely a substance is to react (negatively charged ones tend to be stronger)
Why do some substances only undergo Sn1 reactions
The more complex the substituents = the less empty space around the alpha carbon = the less space a nucleophile has to attach (less chance of Sn2 occurring)
What influences the strength of a leaving group.
It’s pH. The stronger the acid = the weaker the conjugate base = the lower the pKa = the less reactive the substance = the more stable/better leaving group
Relative reactivity group (worst to best leaving groups)
F, Cl, Br and TosO
Sn2 Rate of Reaction Calculation
[leaving group] X [nucleophile]
How Sn2 (bimolecular reactions) is different from Sn1(unimolecular reactions)
Sn2: rate determining step dependent on 2 substances, no intermediate (only transition state), nucleophile has to attach from side opposite leaving group (repulsive forces), primary and some secondary (without benzene rings) alkyl halides undergo Sn2 reactions
How are leaving groups able to leave without the push of a nucleophile in a Sn1 reaction
Due to complexity of other susbstituents leaving group is further away from carbon = further away from attractive forces
What is produced from a chiral Sn1 reaction
racemic mixture
