1
Four carbon-heteroatom bonds : X-C=X,X=C=X,X2C=X,CX4 /
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2
Three carbon-heteroatom bonds : acid halides, carboxylic acids and acid salts /
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3
Three carbon-heteroatom bonds : ester and lactones, peroxy acids and R(CO)OX compounds, R)CO)X,X=S, SE, TE /
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