Following is the structural formula of metformin, the hydrochloride salt of which is mar...

Following is the structural formula of metformin, the hydrochloride salt of which is marketed as the antidiabetic medication Glucophage. Metformin was introduced into clinical practice in the United States in 1995 for the treatment of type 2 diabetes. More than 25 million prescriptions for this drug were written in 2000, making it the most commonly prescribed brand-name diabetes medication in the nation.

(a) Complete the Lewis structure for metformin, showing all valence electrons.

(b) Which nitrogen is the most likely site of protonation?

(c) Draw the structural formula of Glucophage.