The Naked Scientists

The Naked Scientists Forum

Author Topic: how does ethane undergo free redical substitution ander high energy conditions?  (Read 13483 times)

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
how does ethane undergo free redical substitution ander high energy conditions?


 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8669
  • Thanked: 42 times
    • View Profile
What do you know about radical substitution reactions?
Do you know about halogenations for example. These people can draw better pictures than I can.
http://en.wikipedia.org/wiki/Free_radical_halogenation
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
What don't you get?
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
i didnt get if free redical substitution and helogenations is the same.
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Halogenation is just the addition of a halogen(s).
Free radical substitution can be any radical, for example a methyl radical CH3
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
i got you SIR but can you please tell me that for my task they are asking free redical substitution so i dont need to add helogenation right?
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Free radical substitution can include halogenation, like in that link Bored Chemist gave you.
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
thank you for the 1st on
the second one is that how does chloroethane undergoes nucleophillic substitution under fairly mild conditions and elimination under harsher conditions.
i can do how it goes under nucleophillic substitution and elimination but i cant find it in the given conditions.
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Elimination reaction: Something like alcoholic KOH or NaOH should do it.



Substitution reaction: reaction with ammonia will form an amine.

 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
DoH! Did I just write 'warn NH3'! :D
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
its OK
I got that you ment warM
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
how can i evaluate the influence of structure and bonding on the course of reactions in "alkEnes undergo electrophillic addition whereas bezene undergoes electrophillic substitution?
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
For alkenes, what kind of reactivity might we expect form the C=C bond? They have greater electron density than single bonds and they are accessible to external reagents because they are located above and below the plane of the double bond rather than between the nuclei, unlike like a sigma bond. Both electron richness and electron accessibility tells us that the C=C bonds should behave as nucleophiles, this is exactly why most common reactions of alkenes is their reaction with electrophiles. If we have ethene reacting with HCl, the reaction takes place in two steps, beginning with the alkene reacting with H+. Two electrons from ethene move to form a new sigma bond with...arg, my fingers are sore :)

Here: have a picture to see if that'll help



http://upload.wikimedia.org/wikipedia/commons/5/5e/Electrophilic_reaction_of_bromine_with_ethene.png

With benzene, the aromatic rings are less reactive towards nucleophiles than alkenes are. So why does benzene not undergo addition? The simple answer is: If addition occured, the stability of the aromatic ring would be lost, energy would be absorbed, and the overall reaction would be unfavourable. When substitution occurs however, the stability of the aromatic ring is retained, energy is released and the reaction is favourable.
« Last Edit: 12/06/2009 10:52:23 by Chemistry4me »
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
how can i evaluate the influence of structure and bonding on the course of reactions in "alkAnes undergo free redical reactions?"
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
how can i evaluate the influence of structure and bonding on the course of reactions in "the relative reactivities of halogenoalkAnes towards nucleophilic substitution?"
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
how can i evaluate the influence of structure and bonding on the course of reactions in "the relative reactivities of carboxylic acids and acid chlorides towards esterification?"
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
predict the products of the following industrail organic reactions and give the chemical equations involved
i)   dehydration of ethanol using cold concentrated sulfuric acid
ii)  oxidation of ethanol using acidified sodium dichromate solution at room temp
iii) coupling reaction of benzene diazonium chloride with phenyl amine
iv)  refluxing of bezene with concentrated nitric acid and concentrated sulfuric acid

AND then give the reaction mechanisms for reactions given for the each of the above.
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
Look LC
I know I am asking for too much but trust me we don't even know the names of few of the compounds
But still we are asked to do this.
I swear by my life we didn't do any of them in class neither the monster has given us any clue. You tell me what should I do.
In such conditions you are the only one I can ask to help for. :(
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
how can i evaluate the influence of structure and bonding on the course of reactions in "alkAnes undergo free redical reactions?"

They have sigma bonds making the electrons less accessible to outside reactants. It (alkanes) is not particularly reactive so it requires a radical to break the C-H bonds.
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
how can i evaluate the influence of structure and bonding on the course of reactions in "the relative reactivities of halogenoalkAnes towards nucleophilic substitution?"
The halogen atom(s) is more polar than the other atoms, so the nucleophile essentailly 'kicks' it out when it attacks, making the halogen an ion. Because the leaving group (the halogen) is expelled with a neagtive charge in most SN2 reactions, the best leaving groups are those that give the most stable anions, so most of the halogens are good leaving groups. All of these factors contributes to haloalkanes undergoing substitution.
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
how can i evaluate the influence of structure and bonding on the course of reactions in "the relative reactivities of carboxylic acids and acid chlorides towards esterification?"
They both have the carbonyl group C=O, and esters do too. The carbon atom is attached to two highly electronegative atoms, as a result, there is a 'relatively' strong 'slightly positive' charge on the carbon. The non-bonding pair of electrons on the O-H group pf the alcohol attacks the slightly positive Carbon atom, resulting in substitution of the OH- or X- for the alcohol group, forming an ester.
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
i)   dehydration of ethanol using cold concentrated sulfuric acid

http://www.chemguide.co.uk/mechanisms/elim/dhethanol.html

ii)  oxidation of ethanol using acidified sodium dichromate solution at room temp

http://www.chemguide.co.uk/organicprops/alcohols/oxidation.html

iii) coupling reaction of benzene diazonium chloride with phenyl amine

http://www.chemguide.co.uk/organicprops/aniline/propsdiazo.html#top

Scroll down the page a bit, it's down there.

iv)  refluxing of bezene with concentrated nitric acid and concentrated sulfuric acid

http://www.chemguide.co.uk/mechanisms/elsub/nitration.html
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
They've got the mechanisms too.
 

Offline omid

  • Neilep Level Member
  • ******
  • Posts: 1016
    • View Profile
LC
do you have any links for the first three questions?
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
No can do, I'm afriad.
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums