carbonyl group reactivity

[judyfranks6280]

In the Carbonyl Group III video - what is the answer about which aldehyde is more reactive? Acetaldehyde or the aldedhyde with the C-3F group attached? If the aldehyde with the C-3F group has greater reactivity because of inductance but is less reactive because of steric hindrance, which effect wins out?

In general, which has greater influence on any atom, electronegativity or steric hindrance ?

[admin]

The carbonyl group with the C-3F ligand is by far more reactive. It's not even close because of the following: F is not just any electronegative element, it is the MOST electronegative on the periodic table. In addition there are 3 of these extraordinarily electronegative atoms on the C creative an impressive inductive effect.

It is true that there is some degree of increased hindrance but can it be compared to 3X the most EN atom? No, after all, F is not a huge atom (it is the smallest halogen) and, when you look at the molecule, the increase in hindrance does not affect the right side of the molecule (where there is simply a H thus access to the C is still open).

With regards to your second question: "In general, which has greater influence on any atom, electronegativity or steric hindrance ?" There is no simple answer, you must balance the competing influences as described above. However, for the MCAT, it won't be ambiguous, it would be quite clear (ie. pitting rather extremes as described in the example in the video).