Organic Chemistry - Carbanion Question hybridization/valence/geometry

[damnwebassign]

Homework Statement

A carbanion is a species that contains a negatively charged, trivalent carbon.

(a) What is the electronic relationship between a carbanion and a trivalent
nitrogen compound such as NH3?
(b) How many valence electrons does the negatively charged carbon atom
have?
(c) What hybridization do you expect this carbon atom to have?
(d) What geometry is the carbanion likely to have?

Homework Equations

4areas of high electron density = sp3 hybridization
N has 5 valence electrons, C has 4

The Attempt at a Solution

a) The N is neutral while the C has a slight negative charge
b) 8 but so does the N, so why is it negatively charged and not the N
c) sp3
d) trigonal pyramidal 107.5

 

[TeethWhitener]

a) The N is neutral while the C has a slight negative charge

The C has a full negative charge. The important point is in part b, as seen below:

b) 8 but so does the N, so why is it negatively charged and not the N

Because the nuclei of C and N do not have the same charge. Two different compounds with the same valence structure are known as isoelectronic, and certain properties such as geometry tend to be very similar between isoelectronic compounds (another example would be CO carbon monoxide and CN^-, the cyanide anion).

c) sp3

Good. This reflects the fact that carbanions are isoelectronic to sp³-hybridized amine nitrogens.

d) trigonal pyramidal 107.5

Good.