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

✍ Scribed by Volker Schurig; Sabine Reich

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 120 KB
• Volume: 10
• Category: Article
• ISSN: 0899-0042
• DOI: 10.1002/(sici)1520-636x(1998)10:4<316::aid-chir5>3.0.co;2-5

✦ Synopsis

The rotational barriers ⌬G ‡ (T ) of the four atropisomeric polychlorinated biphenyls (PCBs) 2,2Ј,3,5Ј,6-pentachlorobiphenyl (PCB 95), 2,2Ј3,3Ј,4,6Јhexachlorobiphenyl (PCB 132), 2,2Ј,3,3Ј,6,6Ј-hexachlorobiphenyl (PCB 136), and 2,2Ј,3,4Ј,5Ј,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 ⌬G ‡ (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 ⌬G ‡ (T ) of tetrachloro-orthosubstituted PCB 136 is at least (or higher than) 210 kJ/mol at 320°C.