ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: kenhung123 on June 07, 2010, 06:06:40 pm

Title: Alkane substituition
Post by: kenhung123 on June 07, 2010, 06:06:40 pm: Doesn't alkanes react with OH- (NaOH or KOH) to produce alkanol?
Insight said it reacts with water..i thought water was more for addition?
Title: Re: Alkane substituition
Post by: superflya on June 07, 2010, 06:08:16 pm: the preferred pathway is to have a chloroalkane undergo a substitution reaction to form an alkanol.
Title: Re: Alkane substituition
Post by: kyzoo on June 07, 2010, 06:10:56 pm: Quote from: kenhung123 on June 07, 2010, 06:06:40 pm
Insight said it reacts with water..i thought water was more for addition?

I think it does, just that the yield is very very small
Title: Re: Alkane substituition
Post by: kenhung123 on June 07, 2010, 06:18:40 pm: so how does the yield become higher when with water?O.o
Title: Re: Alkane substituition
Post by: chansthename on June 07, 2010, 06:35:15 pm: Quote from: kenhung123 on June 07, 2010, 06:18:40 pm
so how does the yield become higher when with water?O.o
they yield with water is very low
Title: Re: Alkane substituition
Post by: kenhung123 on June 07, 2010, 06:39:37 pm: So am i right then? NaOH+alkane=alkanol?
Title: Re: Alkane substituition
Post by: cindyy on June 07, 2010, 06:41:57 pm: you need to add Cl2 first and then NaOH to make alkanol
Title: Re: Alkane substituition
Post by: chansthename on June 07, 2010, 06:42:39 pm: no, alkane +cl2 -> chloroalkane +hcl

chloroalkane + naoh -> alkanol +nacl

EDIT: http://vcenotes.com/forum/index.php/topic,26404.msg267249.html#msg267249 for my small list of pathways including states.
Title: Re: Alkane substituition
Post by: kenhung123 on June 07, 2010, 06:58:18 pm: ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh damn! yes! sorry guys didn't realise =.=
Title: Re: Alkane substituition
Post by: akira88 on June 07, 2010, 08:13:33 pm: Quote from: kenhung123 on June 07, 2010, 06:58:18 pm
ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh damn! yes! sorry guys didn't realise =.=
Haha I think I did this very same practise exam... is it Insight 2008? Also I think there's something wrong with one of the questions relating to errors in a back titration, from the top of my head I can't remember which question it was. But all I know is that I didn't think the answer was right :S
Title: Re: Alkane substituition
Post by: 8039 on June 07, 2010, 08:29:43 pm: No it doesn't. A catalyst like Chlorine, a halogen, will attack the hydrogen atoms connected to the carbons and substitute them. Then because Cl is highly eletronegative, OH- can sneak up and replace the chlorine, forming an alkanol.
Title: Re: Alkane substituition
Post by: cindyy on June 07, 2010, 08:31:19 pm: Chlorine isnt the catalyst, in a substitution reaction, UV light is the catalyst and that is what provides the energy to break the Cl-Cl bond
Title: Re: Alkane substituition
Post by: 8039 on June 07, 2010, 08:44:19 pm: Quote from: cindyy on June 07, 2010, 08:31:19 pm
Chlorine isnt the catalyst, in a substitution reaction, UV light is the catalyst and that is what provides the energy to break the Cl-Cl bond

Yeah oops, I'm just so used to writing it above the arrow -_-
Title: Re: Alkane substituition
Post by: cindyy on June 07, 2010, 08:46:40 pm: Quote from: 8039 on June 07, 2010, 08:44:19 pm
Quote from: cindyy on June 07, 2010, 08:31:19 pm
Chlorine isnt the catalyst, in a substitution reaction, UV light is the catalyst and that is what provides the energy to break the Cl-Cl bond

Yeah oops, I'm just so used to writing it above the arrow -_-

lol !