Determination of the rotational barriers of atropisomeric polychlorinated biphenyls (PCBs) by a novel stopped-flow multidimensional gas chromatographic technique

• Published in: Chirality (New York, N.Y.) Vol. 10; no. 4; pp. 316 - 320
• Main Authors: Schurig, Volker, Reich, Sabine
• Format: Journal Article
• Language: English
• Published: New York Alan R. Liss, Inc 1998
• Subjects: atropisomeric polychlorinated biphenyls (PCBs); Chirasil-Dex; on-line enantiomerization kinetics; rotational barrier; stopped-flow multidimensional gas chromatographic technique
• ISSN: 0899-0042; 1520-636X
• DOI: 10.1002/(SICI)1520-636X(1998)10:4<316::AID-CHIR5>3.0.CO;2-5

The rotational barriers ΔG‡ (T) of the four atropisomeric polychlorinated biphenyls (PCBs) 2,2′,3,5′,6‐pentachlorobiphenyl (PCB 95), 2,2′3,3′,4,6′‐hexachlorobiphenyl (PCB 132), 2,2′,3,3′,6,6′‐hexachlorobiphenyl (PCB 136), and 2,2′,3,4′,5′,6‐hexachlorobiphenyl (PCB 149) were determined via on‐line enantiomerization kinetics by a new stopped‐flow multidimensional gas chromatographic technique (stopped‐flow MDGC) employing Chirasil‐Dex as chiral stationary phase for enantiomer separation. The calculated rotational barriers ΔG‡ (T) of the trichloro‐ortho‐substituted atropisomers are 184 ± 2 kJ/mol for PCB 95, 189 ± 4 kJ/mol for PCB 132, and 184 ± 1 kJ/mol for PCB 149 at 300°C. The rotational barrier ΔG‡ (T) of tetrachloro‐ortho‐substituted PCB 136 is at least (or higher than) 210 kJ/mol at 320°C. Chirality 10:316–320, 1998. © 1998 Wiley‐Liss, Inc.