Question

. In the zwitterionic (charge separated, + and – formal charges present) resonance form of the amino acid glycine (side chain R = H), the distance from the positively charged amino nitrogen to the negatively charged oxygen atoms on the carboxylate, on the other end of the molecule, is about 3 Å. (a) Sketch a 3D structure, keeping in mind both of the relevant resonance structures, and determine the hybridization scheme used in the σ-bonding framework. (b) Calculate the dipole moment, = . Express your answer in Debye (D). Recall that 1 D = 3.34 × 10./0 C m. The net charge at the two ends of the molecule, and , should be converted to coulombs (C) using the elementary charge = 1.602 × 10.67 C, the charge on an electron or a proton. Use as the distance the distance between the atoms that carry the formal charges and .

Answer 1

Part a

The resonance structures of the zwitter ion is as follows.

3 3

Now for the hybridization, the negatively charged oxygen, the positively charged nitrogen and one carbon are sp³ hybridized, while the double bonded oxygen and the other carbon are sp² hybridized.

sp3 sp2 sp2 H3N sp3 sp3

Part b

The dipole moment can be calculated as,

$\mu =q*r$

where q is the seperated charge and r is the distance. Susbstituting the values and converting them to the appropriate units, we have,

$\mu =\frac{1.602*10^{19}C*3*10^{-10}m*1D}{3.34*10^{-30}Cm}=14.39D$