Ask A Scientist© Chemistry Archive

name         Jim
status       other
age          50s
Question -   What is a coplanar pcb?


I am assuming "pcb" is the acronym for PolyChlorinatedBiphenyl. O.K.?
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A polychlorinated PHENYL is a six member benzene ring with one to 5 H's
replaced by a chlorine. A polychlorinated BIPHENYL is two such benzene rings
bonded together at the sixth position. These BIPHENYLS frequently have a
"propeller shape" because the large Cl atoms sterically interfere with
coplanarity of the benzene rings.  If the two Cl's are located far apart,
say at the 4 position, I suppose the two benzene rings could be coplanar.

A second possible meaning also comes to mind however. An individual PCB
might be "propeller shaped" but in the crystal lattice the molecules may
"stack" in a coplanar configuration.

Vince Calder
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