Year 12s: what will be the first way you research your future options? >>

is Br- a nucleohphile?

Is a Br- ion a nucleophile in the reaction of ethene with a bromine molcule (elctrophillic addition)

The Br- ion I am talking is the one which joins the carbocation which completes the reaction and forms 1,2 dibromoethane

Reply 1

modini

Yes i think so as it is attracted to an area of electron defficiency

Reply 2

Ben_Broadhurst

no it's the electrophile

edit: the first one is, the second is a nucleophile.

Yes

Ben_Broadhurst

no it's the electrophile

NOT

Reply 5

angelmxxx

http://www.chemguide.co.uk/mechanisms/eladd/symbr2.html

the 1st bromine (delta pos.) is an electrophile, which is why the reaction is categoried as "electrophilic addition", but the 2nd (neg.) bromide ion is a nucleophile.

Reply 6

Ben_Broadhurst

wizz_kid

NOT

ok i didn't read the last sentence i thought he was talking about the other one

Reply 7

wizz_kid

Ben_Broadhurst

ok i didn't read the last sentence i thought he was talking about the other one

It is still a nucleophile.

Reply 8

shengoc

Br2 in the presence of alkene, the alkene rich in electron density polarises the bromine molecule, one side delta + and the other delta -. Therefore, it attacks bromine with delta +, giving you a Br- which then acts as a nucleophile and attacks the resulting carbocation from first step - you get dibromoalkane which is colourless.

And yes, Br- is a nucleophile.

Reply 9

Mr. Tizzy XII

Yes. If the entity attacks an area of electron defficiency it is a nucleophile - if an area of high electron density an electrophile. :smile:

Reply 10

Kyle_S-C

There aren't many things with a negative charge that aren't nucleophiles (or bases), they generally want to push the electrons somewhere else or spread them out.

Reply 11

Woody.

Nucleophile - an electron pair donor. You draw the curly arrow from the Br^- to the carbocation, right? Therefore Br^- is an electron pair donor - hence, a nucleophile.