[NewtoAtoms]

Q:  Which one of the following has the greatest equilibrium constant K for cyanohydrin formation?

a. 1
b. 2
c. 3
d. 4
e. 5


I have done all the leg work and I have come to learn that aldehydes have greater equlibrium constants than ketones. Therefore 2,4,5 are eliminated as they are ketones. 

This leaves 1,3.

                          O                                                       OH
                          ll                                                        l
1.  Ch3CH2CH2CH2CH  +  HCN  <---------->  CH3CH2CH2CH2CH
                                                                                   l
                                                                                   CN
                        O                                                H OH
                        ll                                                  l l
3.  CH3Ch2CH2CHCH  +  HCN <---------->  CH3CH2CH2CCH
                     l                                                      l l
                     F                                                    F CN

I also know that increased crowding in the hydrate, decreases K, therefore I would have to conclude that #3 has more crowding, and therefore has a lower equilibrium constant in comparison with #1. 

Am I at all correct? 

Can anyone help me with this difficult question.

Thank you for your time and help

New to Atoms

[nj_bartel]

Aldehydes are more reactive than ketones because they don't have as many electron donating subsituents to stabilize the electron deficient carbonyl carbon.  The electron donating groups in this case are alkyl groups, which are inductively donating.  Is fluorine an inductively electron withdrawing or donating substituent?  How would this effect the stability of the carbonyl?