Cindy Samet

Matrix Isolation Infrared Spectroscopic and Density Functional Theory Study of the 1:1 Complex of Bromocyclohexane with NH3: Evidence for a Weak C–H–N Hydrogen Bond

ABSTRACT The hydrogen-bonded bromocyclohexane–ammonia complex has been isolated and characterized for the first time in argon matrices at 16 K. Coordination of the proton adjacent to the Br substituent on the cyclohexane ring to the amino nitrogen was evidenced by distinct blue shifts of bending modes involving the H-C1–Br unit. In particular, C–C1–Br, H–C1–Br, and C–C1–H bending modes produced blue shifts ranging from 2.8 to 12.2 cm−1. Density Functional Theory (DFT) calculations at the B3LYP/6–31 + G(d, p) level yield an essentially linear Br–C1–H–NH3 hydrogen bond with a C-H–N distance of 2.412 Å and a hydrogen bond energy of 2.95 kcal/mol.

Determination of the Regiochemistry of Disubstituted Arenes Generated by Addition of a Carbanion to the (η6-Anisole)Cr(CO)3 Complex

It has become increasingly important to demonstrate to undergraduates that chemistry is not many separate subfields, but rather a set of interconnected concepts. We describe a laboratory activity that integrates fundamental concepts of organic and organometallic chemistry and then employs standard instrumental techniques (GC) and molecular modeling to justify the results. Students synthesize the (η6-anisole)Cr(CO)3 complex and react it with the -:CH2CN anion to generate methoxyphenylacetonitrile. They then determine the relative amounts of the three possible regioisomers of the disubstituted arene using GC. We have shown this synthesis to be straightforward for students to accomplish, with results that are reproducible.