(A) Melamine is a carbon–hydrogen–nitrogen compound used in the manufacture of adhesives, protective coatings, and textile finishing (such as in wrinkle-free, wash-and-wear fabrics). Its mass percent composition is 28.57% C, 4.80% H, and 66.64% N. The melamine molecule features a six-member ring with alternating carbon and nitrogen atoms. Half the nitrogen atoms and all the H atoms are outside the ring. For melamine, 

(a) Write a plausible Lewis structure, 

(b) Describe bonding in the molecule by the valence bond method, and 

(c) Describe bonding in the ring system through molecular orbital theory.

(B) Dimethylglyoxime (DMG) is a carbon–hydrogen–nitrogen–oxygen compound with a molecular mass of 116.12 u. In a combustion analysis, a 2.464 g sample of DMG yields 3.735 g CO₂ and 1.530 g H₂O. In a separate experiment, the nitrogen in a 1.868 g sample of DMG is converted to NH₃(g) and the NH₃ is neutralized by passing it into 50.00 mL of 0.3600 M H₂SO₄(aq). After neutralization of the NH₃ the excess H₂SO₄(aq) requires 18.63 mL of 0.2050 M NaOH(aq) for its neutralization. Using these data, determine for dimethylglyoxime 

(a) The most plausible Lewis structure, and 

(b) In the manner of Figure 11-19, a plausible bonding scheme.

Figure 11-19

Transcribed Image Text:

T: С(2p)-0(2p) H o: H(1s)-C(sp²) 120°C= H 120⁰ o: C(sp²)-0(2p) [or, o: C(sp²)-0(sp²)]