POLYCHLORINATED BIPHENYLS (PCB's) - Environmental Implications

NOMENCLATURE OF PCB's

PCB's are the class of synthetic chlorinated organic compounds constituting biphenyl as the basic structural unit. Chlorination of the group can produce 209 possible chlorobiphenyls (congeners) substituted with 1 to 10 chlorine atoms. Systematic numbering and nomenclature of these chlorobiphenyls according to Ballschmiter and Zell are given in the Table 1. According to the IUPAC nomenclature of organic chemistry the structure of PCB's constitute two rings, one ring in the biphenyl assembly is assigned unprimed number and the other biphenyl assembly as primed numbers (Fig. 1).

Fig. 1: Structure and numbering pattern of PCB's in biphenyl ring system
As per the IUPAC system, the order for assigning priorities to the substituents in the ring assembly, as Chlorine in PCB's are:
  • Unprimed number is assigned lower order than the corresponding primed number as 2 vs. 2'.
  • Lower number is assigned to a point of attachment in equivalent position, as 2 vs. 6, for the substituents in one of the ortho positions.
  • When the number of substituents in the two ring systems is the same, unprimed numbers are assigned to the ring system with smaller numbered substituents.
The increased use of PCB's as important industrial chemicals for use as non-flammable oils in a host of products gave birth to a series of commercially available raw materials marketed under various trade names. The trade names of commonly used PCB based commercial/industrial dielectric fluids are presented in Table 2.

Table 1 Polychlorinated Biphenyl (PCB's) congeners/isomers and their nomenclature as per IUPAC System

Group

BZ* No.

PCB Congener/Isomers

CAS Registry No.

Monochloro-biphenyl

BZ-1

2-Chlorobiphenyl

2051-60-7

BZ-2

3-Chlorobiphenyl

2051-61-8

BZ-3

4-Chlorobiphenyl

2051-62-9

Dichloro-biphenyl

BZ-4

2,2’-Dichlorobiphenyl

13029-08-8

BZ-5

2,3-Dichlorobiphenyl

16605-91-7

BZ-6

2,3’-Dichlorobiphenyl

25569-80-6

BZ-7

2,4-Dichlorobiphenyl

33284-50-3

BZ-8

2,4’-Dichlorobiphenyl

34883-43-7

BZ-9

2,5-Dichlorobiphenyl

34883-39-1

BZ-10

2,6-Dichlorobiphenyl

33146-45-1

BZ-11

3,3’-Dichlorobiphenyl

2050-67-1

BZ-12

3,4-Dichlorobiphenyl

2974-92-7

BZ-13

3,4’-Dichlorobiphenyl

2974-90-5

BZ-14

3,5-Dichlorobiphenyl

34883-41-5

BZ-15

4,4’-Dichlorobiphenyl

2050-68-2

Trichloro-biphenyl

BZ-16

2,2’,3-Trichlorobiphenyl

38444-78-9

BZ-17

2,2’,4-Trichlorobiphenyl

37680-66-3

BZ-18

2,2’,5-Trichlorobiphenyl

37680-65-2

BZ-19

2,2’,6-Trichlorobiphenyl

38444-73-4

BZ-20

2,3,3’-Trichlorobiphenyl

38444-84-7

BZ-21

2,3,4-Trichlorobiphenyl

55702-46-0

BZ-22

2,3,4’-Trichlorobiphenyl

38444-85-8

BZ-23

2,3,5-Trichlorobiphenyl

55720-44-0

BZ-24

2,3,6-Trichlorobiphenyl

55702-45-9

BZ-25

2,3’,4-Trichlorobiphenyl

55712-37-3

BZ-26

2,3’,5-Trichlorobiphenyl

38444-81-4

BZ-27

2,3’,6-Trichlorobiphenyl

38444-76-7

BZ-28

2,4,4’-Trichlorobiphenyl

7012-37-5

BZ-29

2,4,5-Trichlorobiphenyl

15862-07-4

BZ-30

2,4,6-Trichlorobiphenyl

35693-92-6

BZ-31

2,4’,5-Trichlorobiphenyl

16606-02-3

BZ-32

2,4’,6-Trichlorobiphenyl

38444-77-4

BZ-33

2’,3,4-Trichlorobiphenyl

38444-86-9

BZ-34

2’,3,5-Trichlorobiphenyl

37680-68-5

BZ-35

3,3’,4-Trichlorobiphenyl

37680-69-6

BZ-36

3,3’,5-Trichlorobiphenyl

38444-87-0

BZ-37

3,4,4’-Trichlorobiphenyl

38444-90-5

BZ-38

3,4,5-Trichlorobiphenyl

53555-66-1

BZ-39

3,4’,5-Trichlorobiphenyl

38444-88-1

Tetrachloro-biphenyl

BZ-40

2,2’,3,3’-Tetrachlorobiphenyl

38444-93-8

BZ-41

2,2’,3,4-Tetrachlorobiphenyl

52663-59-9

BZ-42

2,2’,3,4’-Tetrachlorobiphenyl

36559-22-5

BZ-43

2,2’,3,5-Tetrachlorobiphenyl

70362-46-8

BZ-44

2,2’,3,5’-Tetrachlorobiphenyl

41464-39-5

BZ-45

2,2’,3,6-Tetrachlorobiphenyl

70362-45-7

BZ-46

2,2’,3,6’-Tetrachlorobiphenyl

41464-47-5

BZ-47

2,2’,4,4’-Tetrachlorobiphenyl

2437-79-8

BZ-48

2,2’,4,5-Tetrachlorobiphenyl

70362-47-9

BZ-49

2,2’,4,5’-Tetrachlorobiphenyl

41464-40-8

BZ-50

2,2’,4,6-Tetrachlorobiphenyl

62796-65-0

BZ-51

2,2’,4,6’-Tetrachlorobiphenyl

68194-04-7

BZ-52

2,2’,5,5’-Tetrachlorobiphenyl

35693-99-3

BZ-53

2,2’,5,6’-Tetrachlorobiphenyl

41464-41-9

BZ-54

2,2’,6,6’-Tetrachlorobiphenyl

15968-05-5

BZ-55

2,3,3’,4-Tetrachlorobiphenyl

74338-24-2

BZ-56

2,3,3’,4’-Tetrachlorobiphenyl

41464-43-1

BZ-57

2,3,3’,5-Tetrachlorobiphenyl

70424-67-8

BZ-58

2,3,3’,5’-Tetrachlorobiphenyl

41464-49-7

BZ-59

2,3,3’,6-Tetrachlorobiphenyl

74472-33-6

BZ-60

2,3,4,4’-Tetrachlorobiphenyl

33025-41-1

BZ-61

2,3,4,5-Tetrachlorobiphenyl

33284-53-6

BZ-62

2,3,4,6-Tetrachlorobiphenyl

54230-22-7

Group

BZ* No.

PCB Congener/Isomers

CAS Registry No.

Tetrachloro-biphenyl

BZ-63

2,3,4’,5-Tetrachlorobiphenyl

74472-34-7

BZ-64

2,3,4’,6-Tetrachlorobiphenyl

52663-58-8

BZ-65

2,3,5,6-Tetrachlorobiphenyl

33284-54-7

BZ-66

2,3’,4,4’-Tetrachlorobiphenyl

32598-10-0

BZ-67

2,3’,4,5-Tetrachlorobiphenyl

73557-53-8

BZ-68

2,3’,4,5’-Tetrachlorobiphenyl

73575-52-7

BZ-69

2,3’,4,6-Tetrachlorobiphenyl

60233-24-1

BZ-70

2,3’,4’,5-Tetrachlorobiphenyl

32598-11-1

BZ-71

2,3’,4’,6-Tetrachlorobiphenyl

41464-46-4

BZ-72

2,3’,5,5’-Tetrachlorobiphenyl

41464-42-0

BZ-73

2,3’,5’,6-Tetrachlorobiphenyl

74338-23-1

BZ-74

2,4,4’,5-Tetrachlorobiphenyl

32690-93-0

BZ-75

2,4,4’,6-Tetrachlorobiphenyl

32598-12-2

BZ-76

2’,3,4,5-Tetrachlorobiphenyl

70362-48-0

BZ-77

3,3’,4,4’-Tetrachlorobiphenyl

32598-13-3

BZ-78

3,3’,4,5-Tetrachlorobiphenyl

70362-49-1

BZ-79

3,3’,4,5’-Tetrachlorobiphenyl

41464-48-6

BZ-80

3,3’,5,5’-Tetrachlorobiphenyl

33284-52-5

BZ-81

3,4,4’,5-Tetrachlorobiphenyl

70362-50-4

Pentachloro-biphenyl

BZ-82

2,2’,3,3’,4-Pentachlorobiphenyl

52663-62-4

BZ-83

2,2’,3,3’,5-Pentachlorobiphenyl

60145-20-2

BZ-84

2,2’,3,3’,6-Pentachlorobiphenyl

52663-60-2

BZ-85

2,2’,3,4,4’-Pentachlorobiphenyl

65510-45-4

BZ-86

2,2’,3,4,5-Pentachlorobiphenyl

55312-69-1

BZ-87

2,2’,3,4,5’-Pentachlorobiphenyl

38380-02-8

BZ-88

2,2’,3,4,6-Pentachlorobiphenyl

55215-17-3

BZ-89

2,2’,3,4,6’-Pentachlorobiphenyl

73575-57-2

BZ-90

2,2’,3,4’,5-Pentachlorobiphenyl

68194-07-0

BZ-91

2,2’,3,4’,6-Pentachlorobiphenyl

68194-05-8

BZ-92

2,2’,3,5,5’-Pentachlorobiphenyl

52663-61-3

BZ-93

2,2’,3,5,6-Pentachlorobiphenyl

73575-56-1

BZ-94

2,2’,3,5,6’-Pentachlorobiphenyl

73575-55-0

BZ-95

2,2’,3,5’,6-Pentachlorobiphenyl

38379-99-6

BZ-96

2,2’,3,6,6’-Pentachlorobiphenyl

73575-54-9

BZ-97

2,2’,3’,4,5-Pentachlorobiphenyl

41464-51-1

BZ-98

2,2’,3’,4,6-Pentachlorobiphenyl

60233-25-2

BZ-99

2,2’,4,4’,5-Pentachlorobiphenyl

38380-01-7

BZ-100

2,2’,4,4’,6-Pentachlorobiphenyl

39485-83-1

BZ-101

2,2’,4,5,5’-Pentachlorobiphenyl

37680-73-2

BZ-102

2,2’,4,5,6’-Pentachlorobiphenyl

68194-06-9

BZ-103

2,2’,4,5’,6-Pentachlorobiphenyl

60145-21-3

BZ-104

2,2’,4,6,6’-Pentachlorobiphenyl

56558-16-8

BZ-105

2,3,3’,4,4’-Pentachlorobiphenyl

32598-14-4

BZ-106

2,3,3’,4,5-Pentachlorobiphenyl

70424-69-0

BZ-107

2,3,3’,4’,5-Pentachlorobiphenyl

70424-68-9

BZ-108

2,3,3’,4,5’-Pentachlorobiphenyl

70362-41-3

BZ-109

2,3,3’,4,6-Pentachlorobiphenyl

74472-35-8

BZ-110

2,3,3’,4’,6-Pentachlorobiphenyl

38380-03-9

BZ-111

2,3,3’,5,5’-Pentachlorobiphenyl

39635-32-0

BZ-112

2,3,3’,5,6-Pentachlorobiphenyl

74472-36-9

BZ-113

2,3,3’,5’,6-Pentachlorobiphenyl

68194-10-5

BZ-114

2,3,4,4’,5-Pentachlorobiphenyl

74472-37-0

BZ-115

2,3,4,4’,6-Pentachlorobiphenyl

74472-38-1

BZ-116

2,3,4,5,6-Pentachlorobiphenyl

18259-05-7

BZ-117

2,3,4’,5,6-Pentachlorobiphenyl

68194-11-6

BZ-118

2,3’,4,4’,5-Pentachlorobiphenyl

31508-00-6

BZ-119

2,3’,4,4’,6-Pentachlorobiphenyl

56558-17-9

BZ-120

2,3’,4,5,5’-Pentachlorobiphenyl

68194-12-7

BZ-121

2,3’,4,5’,6-Pentachlorobiphenyl

56558-18-0

BZ-122

2’,3,3’,4,5-Pentachlorobiphenyl

76842-07-4

BZ-123

2’,3,4,4’,5-Pentachlorobiphenyl

65510-44-3

BZ-124

2’,3,4,5,5’-Pentachlorobiphenyl

70424-70-3

BZ-125

2’,3,4,5,6’-Pentachlorobiphenyl

74472-39-2

BZ-126

3,3’,4,4’,5-Pentachlorobiphenyl

57465-28-8

 

BZ-127

3,3’,4,5,5’-Pentachlorobiphenyl

39635-33-1

Group

BZ* No.

PCB Congener/Isomers

CAS Registry No.

Hexachloro-biphenyl

BZ-128

2,2’,3,3’,4,4’-Hexachlorobiphenyl

38380-07-3

BZ-129

2,2’,3,3’,4,5-Hexachlorobiphenyl

55215-18-4

BZ-130

2,2’,3,3’,4,5’-Hexachlorobiphenyl

52663-66-8

BZ-131

2,2’,3,3’,4,6-Hexachlorobiphenyl

61798-70-7

BZ-132

2,2’,3,3’,4,6’-Hexachlorobiphenyl

38380-05-1

BZ-133

2,2’,3,3’,5,5’-Hexachlorobiphenyl

35694-04-3

BZ-134

2,2’,3,3’,5,6-Hexachlorobiphenyl

52704-70-8

BZ-135

2,2’,3,3’,5,6’-Hexachlorobiphenyl

52744-13-5

BZ-136

2,2’,3,3’,6,6’-Hexachlorobiphenyl

38411-22-2

BZ-137

2,2’,3,4,4’,5-Hexachlorobiphenyl

35694-06-5

BZ-138

2,2’,3,4,4’,5’-Hexachlorobiphenyl

35065-28-2

BZ-139

2,2’,3,4,4’,6-Hexachlorobiphenyl

56030-56-9

BZ-140

2,2’,3,4,4’,6’-Hexachlorobiphenyl

59291-64-4

BZ-141

2,2’,3,4,5,5’-Hexachlorobiphenyl

52712-04-6

BZ-142

2,2’,3,4,5,6-Hexachlorobiphenyl

41411-61-4

BZ-143

2,2’,3,4,5,6’-Hexachlorobiphenyl

68194-15-0

BZ-144

2,2’,3,4,5’,6-Hexachlorobiphenyl

68194-14-9

BZ-145

2,2’,3,4,6,6’-Hexachlorobiphenyl

74472-40-5

BZ-146

2,2’,3,4’,5,5’-Hexachlorobiphenyl

51908-16-8

BZ-147

2,2’,3,4’,5,6-Hexachlorobiphenyl

68194-13-8

BZ-148

2,2’,3,4’,5,6’-Hexachlorobiphenyl

74472-41-6

BZ-149

2,2’,3,4’,5’,6-Hexachlorobiphenyl

38380-04-0

BZ-150

2,2’,3,4’,6,6’-Hexachlorobiphenyl

68194-08-1

BZ-151

2,2’,3,5,5’,6-Hexachlorobiphenyl

52663-63-5

BZ-152

2,2’,3,5,6,6’-Hexachlorobiphenyl

68194-09-2

BZ-153

2,2’,4,4’,5,5’-Hexachlorobiphenyl

35065-27-1

BZ-154

2,2’,4,4’,5,6’-Hexachlorobiphenyl

60145-22-4

BZ-155

2,2’,4,4’,6,6’-Hexachlorobiphenyl

33979-03-2

BZ-156

2,3,3’,4,4’,5-Hexachlorobiphenyl

38380-08-4

BZ-157

2,3,3’,4,4’,5’-Hexachlorobiphenyl

69782-90-7

BZ-158

2,3,3’,4,4’,6-Hexachlorobiphenyl

74472-42-7

BZ-159

2,3,3’,4,5,5’-Hexachlorobiphenyl

39635-35-3

BZ-160

2,3,3’,4,5,6-Hexachlorobiphenyl

41411-62-5

BZ-161

2,3,3’,4,5’,6-Hexachlorobiphenyl

74474-43-8

BZ-162

2,3,3’,4’,5,5’-Hexachlorobiphenyl

39635-34-2

BZ-163

2,3,3’,4’,5,6-Hexachlorobiphenyl

74472-44-9

BZ-164

2,3,3’,4’,5’,6-Hexachlorobiphenyl

74472-45-0

BZ-165

2,3,3’,5,5’,6-Hexachlorobiphenyl

74472-46-1

BZ-166

2,3,4,4’,5,6-Hexachlorobiphenyl

41411-63-6

BZ-167

2,3’,4,4’,5,5’-Hexachlorobiphenyl

52663-72-6

BZ-168

2,3’,4,4’,5’,6-Hexachlorobiphenyl

59291-65-5

BZ-169

3,3’,4,4’,5,5’-Hexachlorobiphenyl

32774-16-6

 

Heptachloro-biphenyl

BZ-170

2,2’,3,3’,4,4’,5-Heptachlorobiphenyl

35065-30-6

BZ-171

2,2’,3,3’,4,4’,6-Heptachlorobiphenyl

52663-71-5

BZ-172

2,2’,3,3’,4,5,5’-Heptachlorobiphenyl

52663-74-8

BZ-173

2,2’,3,3’,4,5,6-Heptachlorobiphenyl

68194-16-1

BZ-174

2,2’,3,3’,4,5,6’-Heptachlorobiphenyl

38411-25-5

BZ-175

2,2’,3,3’,4,5’,6-Heptachlorobiphenyl

40186-70-7

BZ-176

2,2’,3,3’,4,6,6’-Heptachlorobiphenyl

52663-65-7

BZ-177

2,2’,3,3’,4’,5,6-Heptachlorobiphenyl

52663-70-4

BZ-178

2,2’,3,3’,5,5’,6-Heptachlorobiphenyl

52663-67-9

BZ-179

2,2’,3,3’,5,6,6’-Heptachlorobiphenyl

52663-64-6

BZ-180

2,2’,3,4,4’,5,5’-Heptachlorobiphenyl

35065-29-3

BZ-181

2,2’,3,4,4’,5,6-Heptachlorobiphenyl

74472-47-2

BZ-182

2,2’,3,4,4’,5,6’-Heptachlorobiphenyl

60145-23-5

BZ-183

2,2’,3,4,4’,5’,6-Heptachlorobiphenyl

52663-69-1

BZ-184

2,2’,3,4,4’,6,6’-Heptachlorobiphenyl

74472-48-3

BZ-185

2,2’,3,4,5,5’,6-Heptachlorobiphenyl

52712-05-7

BZ-186

2,2’,3,4,5,6,6’-Heptachlorobiphenyl

74472-49-4

BZ-187

2,2’,3,4’,5,5’,6-Heptachlorobiphenyl

52663-68-0

BZ-188

2,2’,3,4’,5,6,6’-Heptachlorobiphenyl

74487-85-7

BZ-189

2,3,3’,4,4’,5,5’-Heptachlorobiphenyl

39635-31-9

BZ-190

2,3,3’,4,4’,5,6-Heptachlorobiphenyl

41411-64-7

 

BZ-191

2,3,3’,4,4’,5’,6-Heptachlorobiphenyl

74472-50-7

BZ-192

2,3,3’,4,5,5’,6-Heptachlorobiphenyl

74472-51-8

BZ-193

2,3,3’,4’,5,5’,6-Heptachlorobiphenyl

69782-91-8

Group

BZ* No.

PCB Congener/Isomers

CAS Registry No.

Octachloro-biphenyl

BZ-194

2,2’,3,3’,4,4’,5,5’-Octachlorobiphenyl

35694-08-7

BZ-195

2,2’,3,3’,4,4’,5,6-Octachlorobiphenyl

52663-78-2

BZ-196

2,2’,3,3’,4,4’,5’,6-Octachlorobiphenyl

42740-50-1

BZ-197

2,2’,3,3’,4,4’,6,6’-Octachlorobiphenyl

33091-17-7

BZ-198

2,2’,3,3’,4,5,5’,6-Octachlorobiphenyl

68194-17-2

BZ-199

2,2’,3,3’,4,5,6,6’-Octachlorobiphenyl

52663-73-7

BZ-200

2,2’,3,3’,4,5’,6,6’-Octachlorobiphenyl

40186-71-8

BZ-201

2,2’,3,3’,4,5,5’,6’-Octachlorobiphenyl

52663-75-9

BZ-202

2,2’,3,3’,5,5’,6,6’-Octachlorobiphenyl

2136-99-4

BZ-203

2,2’,3,4,4’,5,5’,6-Octachlorobiphenyl

52663-76-0

BZ-204

2,2’,3,4,4’,5,6,6’-Octachlorobiphenyl

74472-52-9

BZ-205

2,3,3’,4,4’,5,5’,6-Octachlorobiphenyl

74472-53-0

Nonachloro-biphenyl

BZ-206

2,2’,3,3’,4,4’,5,5’,6-Nonachlorobiphenyl

40186-72-9

BZ-207

2,2’,3,3’,4,4’,5,6,6’-Nonachlorobiphenyl

52663-79-3

BZ-208

2,2’,3,3’,4,5,5’,6,6’-Nonachlorobiphenyl

52663-77-1

Decachloro-biphenyl

BZ-209

2,2’,3,3’,4,4’,5,5’,6,6’- Decachlorobiphenyl

2051-24-3

*  BZ : Ballschmiter and Zell Number

Table 2 Commercial Trade names of PCB's/PCT's based Commercial/Industrial Dielectric Fluids

Country

Commercial Name

Remarks

United Kingdom (U.K.)

Aroclor

-

Pyroclor

-

Santothern*

Used for Heat Transfer

USA

Aroclor

-

Inerteen

-

Pyranol

-

Therminol FR*

Used for Heat Transfer

Pydraul

Used for Hydraulic Application before 1972

France

Pyralene

-

Phenoclor

-

Germany

Clophen

-

Italy

Apirolio

-

Fenoclor

-

Japan

Kaneclor

-

Russia (Earlier USSR)

Solvol

-

* FR Series of Santothern and Therminol contain PCB's and were used prior to 1972.