IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: aiyla on October 15, 2009, 11:02:12 am

Title: some chemistry Questions help please
Post by: aiyla on October 15, 2009, 11:02:12 am

I got these Questions that i don't know how to answer in a proper way, as an AS level student answer.
so can anyone answer these for me ?

Q1- discuss completely the reaction of HBr with propene . [4]
Q2- what happens when bromine reacts with ethene?, give the mechanism of the reaction. [3]
Q3-what conditions are necessary to manufacture low density poly ethene? ,why it is useful ? [2]
4- write down the structural formula of
     a) Teflon
     b) poly venylethene
     c) PVC
4-b . give the systemic name of the following compounds

1) (http://i37.tinypic.com/2cshyrc.jpg)

2) (http://i35.tinypic.com/244y2pu.jpg)

3) (http://i34.tinypic.com/23uq4x4.jpg)


i don't know where these Questions are from they were given by my teacher .

Title: Re: some chemistry Questions help please
Post by: Light on October 17, 2009, 03:58:41 am

Q1:the reaction of HBr and propene is electrophilic addition.The H in HBr has positive dipoles and Br has negative dipoles.The double bond in propene which is nucleophilic attack the HBr bond and The H ions attach to the carbon atom with more hydrogen group according to Markonikoff rule.A carbocation is formed as intermediate.The Br, as electrophile,bind to carbocation and form 1-bromopropane.

Q2:One side of Br will has postive dipoles and other side of Br has negative dipoles.The highly negative double bond attack the bromine molecule and a carbocation is formed.The Br which is poor in electrons will then attack the carbocation and form 1,2-bromoethane.Electrophilic addition mechanism.


Want more????

Title: Re: some chemistry Questions help please
Post by: aiyla on October 17, 2009, 09:20:11 am

thanks,, thats awesome answers .
if its no bother to you .. why, not please ?

Title: Re: some chemistry Questions help please
Post by: nid404 on October 17, 2009, 09:22:45 am

Quote from: aiyla on October 17, 2009, 09:20:11 am

thanks,, thats awesome answers .
if its no bother to you .. why, not please ?

sorry i haven't done organic chemistry as yet

Title: Re: some chemistry Questions help please
Post by: Light on October 17, 2009, 10:08:40 am

Q3:high pressure via free radical polymerisation.Excellent resistance (no attack) to dilute and concentrated acids, alcohols, bases and esters
Good resistance (minor attack) to aldehydes, ketones and vegetable oils .

Q4:a) F2C=CF2
b)no such thing. only heard before phenylethene .
c)CH2=CHCl

4b 1)2-methylbut-1-ene
2)2-ethylpent-1-ene
3)2-methylprop-1-ene



Light's copyright.

Title: Re: some chemistry Questions help please
Post by: nid404 on October 17, 2009, 10:44:10 am

thanks for answering :)