Organic Chemistry - ORGANIC : ring expansion

1

voldy ·2009-02-27 05:40:40

gagar then major one will be one with five membered ring no ?

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iitimcomin ·2009-02-25 21:33:33

and bhiyya if i do the same with a 3 member ring will it expand ????????

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iitimcomin ·2009-02-25 21:35:50

cuz i dont see exceptional stability in 3 member ring like the 6 member 1!!!!!![2][2]

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iitimcomin ·2009-02-25 22:55:13

heeeelllllllllllpppppppppppppppp pme bhiyyaaaaa!!!!!!!!!!!!!!!!!!!!!![2][2]2[2][2][2][2][2]

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62

Lokesh Verma ·2009-02-25 23:00:53

but the strain reduces a lot..

see here the carbon is sp³ hybridised.

so the bond angle should be 108-9 degree..

but the geometry causes it to be at 60!

so there is a lto fo strain.

In going to a 4 carbon ring structure most of the strain is gone..
so there is huge energy released and thus more stability.

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62

Lokesh Verma ·2009-02-25 23:08:36

This is what I think should have happened in that case iitimcoming..

your analysis for the 3 membered structure seems correct

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1

gagar.iitk ·2009-02-27 04:12:44

@ nishant i am also thinking of any shortcut method for this conversion but not getting any although by breaking the ring and then using LDA for directed aldol would bring the seven membered ring

if u got any shorter one plz let me know

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62

Lokesh Verma ·2009-02-27 04:26:36

hmm.. okie..

you expect me to know that even when you dont.. ;)

but in case (wich is most unlikely.. ) if i do.. i will try to..

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21

tapanmast Vora ·2009-02-27 04:43:15

sir, how will u brek the ring??? Favorskii ??

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gagar.iitk ·2009-02-27 04:55:03

bringing double bond in the cycle and reduced ozonolysis

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iitimcomin ·2009-02-25 21:29:27

im unable to understand how to make it a 3Â° carbocation....pls help[2][2][2][2]

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1

gagar.iitk ·2009-02-27 05:44:37

SRINATH THATS WHY I AM USING LDA FOR DIRECTED ALDOL THIS WILL GIVE SEVEN MEMBERED RING EXCLUSIVELY (i am using the word exclusive b'cos in case of LDA we form only one product)

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1

voldy ·2009-02-27 05:47:05

LDA is for abstracting less sterically hindered H no ?

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gagar.iitk ·2009-02-27 05:47:47

very true

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voldy ·2009-02-27 05:49:50

ok thankx.

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prateek punj ·2009-02-27 05:52:34

bhaiya in pinacol-pinacolone there we can have ring expansion.....

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prateek punj ·2009-02-27 05:54:17

can we use this method....

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gagar.iitk ·2009-02-27 05:54:53

a lenthier process and i am trying to make it shorter

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prateek punj ·2009-02-27 05:55:45

okey....

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voldy ·2009-02-25 05:59:13

well tapan this method can be used here try to bring NH2 grp at the methyl thing then demayjanov ring expansion I dunno abt yield seven membered ring no?