IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry - HC [admin]: Hyper conjugation and its consequence

arvind1990

What do you mean by Hyper conjugation and what is its consequence??

Can anyone explain me with an example??

rashmi_jain

hyper conjugation is the delocalisation of sigma electron.it is also called sigma-pi conjugation or no bond resonance.

occurence- alkenes,alkynes,free radicals(saturated type),carbonium ions(saturated type).

condition: presence of

-H with repect to double bond,triple bond,carbon containing positive charge or unpaired electron(free radical).

H H⁺

| _

H-CH-CH=CH₂

H-CH=CH-CH₂

similarily for other two

-H atoms.

number of hyperconjugative structures=number of

-H atoms.

effects:

1)effects the bond length like resonance.

2)affects dipole moment due to formation of charges.

3)stability of carbonium ions and free radicals:more the number of hyperconjugative structures,more is the stability

arvind1990

you have said,"similarily for other two

-H atoms".

What does this mean?.Is it referring to the two

-H atoms which is present in the left of the double bond or two that is present in the right.

How does hyper conjugation affect the chemical properties of a compound??

bubun

Other 2 alpha atoms means those in the original compound

H

I

H - C - CH=CH₂

I

H

The H shown will participate in hyperconjugation

arvind1990

why can't alpha H present on the right side of the double bond(i.e.,CH2)

participate in Hyperconjugation

bubun

a-H are the ones which are attached to a-C on the right there is no a-C . The C attached next to the C=C is the a-C next to that is b-C