Question

How do I know, if (S)-2-bromobutane reacts with iodid (I-) SN1 or SN2? So how can I sepperate those competitive Reactions, when it comes to a secondary Carbonatom?

Answer 1

1 degree halogenoalkanes follow SN2 reactions

Answer 2

3 degree halogenoalkanes follow SN1 reactions

Answer 3

in SN2 type reactions the rate of reaction depends on conc of halogoalkane and neuclophile

Answer 4

in SN1 type reaction the rate of reaction depends on conc of halogenoalkane only

Answer 5

it will follow SN2 type machenism

Answer 6

So when a halogenoalkane reacts with another halogen, it will be SN2. I didn't get how to sepperate point 3 and 4, when it comes to the concentration, because how do I know if I need a high concentration of the nucleophile?

Answer 7

you want only one reaction i.e either SN1 or SN2 reaction to happen with your secondary halide..
is this what you want?

Answer 8

to separate an SN1 reaction from an SN2 reaction, the only way conceieveable is the concentration of nucleophille.

for the conc. of nucleophille is the only point of difference between SN1 and an SN2 reaction for a same alkyl halide.

Answer 9

But how do I know the concentration? The task is a copy of the exams task: "How does a reaction proceed for (S)-2-bromobutane with iodid?" There is nothing said about a concentration...

Answer 10

you need not know the con. exactly and precisely for this.

you know that in an SN2 reaction, the rate is dependent on the nucleophile too.

So, if the nucleophile is strong then it will go through SN2 mechanism.
strong nucleophile as in CH3O- ( methoxide)

Answer 11

the nature of solvent we choose will also influence the path with which the reaction might proceed.

Answer 12

But by knowing the nucleophile (I is, as I would argue because it's position in the PSE, a strong nucleophile) I also can say this is going to be a SN2 reaction, can't I?

Answer 13

yes you can say that.
but i must say that SN2 will be slightly larger only.

but if we choose some polar solvent then we can increase SN2's amount.

the trick lies in identifying the points of differences between SN1 and SN2 and using them to increase the rate of one reaction over the other

Answer 14

Ok, thank you :)