[AdiDex]

I have doubt about charge distribution and reactivity .
When Acid catalysed Ring opening of unsymmetrical epoxide take place we say that nucleophile will attack on the carbon which is more substituted . Since there will be more charge ,as alkyl groups helps in charge stabilization .

But someday before i read about Dipole moment of Formaldehyde and Acetone . Intially I knew from High School that Acetone is bigger molecule than Formaldehyde therefore it's dipole moment is greater .
But Now I read that in acetone there is positive charge stabilization due to methyl groups , which lead to more  charge seperation between O and C , since now Carbon can accumulate more charge because Methyl can stablize it .
I have checked IR abosprtion data of carbonyl , acetone has lesser stretching frequency , which implies that the bond between C and O is weaker than in case of formaldehyde .So according to this Carbon should has more charge .
So this is supporting what i have read few days ago .
Q.1 Should we say that due to charge stabilization  or due to it is bigger , Acetone has greater dipole moment than Acetaldehyde (1 methyl ) greater than formaldehyde (no methyl). Which is major factor ?

Q.2 if carbon has more charge density in case of acetone , then why it is not that much electrophilic as it is in formaldehyde .

I know that every reaction is govern by 3 factors
1) Steric
2) Charge
3) orbital interaction

So in case of carbonyl , is orbital energy and interaction is more important ? And in case of acid catalysed unsymmetrical ring opening of epoxides the charge is more important ?

[AdiDex]

[AdiDex]

is my question irrelevant ?? atleast give me some reply please . Is my understanding is totally wrong ??

[rolnor]

I am thinking, if you use a bigger alcohol, let say 2-propanol and acid catalyst, would steric effects force the epoxide to open on the less substituted side? Maby at least partialy.

[AdiDex]

My Question is for H₂O and reason of Electrophilicity of the epoxide .