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naphthyl group

American  
[naf-thil groop, nap-thil] / ˈnæf θɪl ˌgrup, ˈnæp θɪl /

noun

Chemistry.
  1. Also called alpha-naphthyl group.  Also called alpha-naphthyl radical.  the univalent group C 1 0 H 7 –, having a replaceable hydrogen atom in the first, or alpha, position; 1-naphthyl group.

  2. Also called beta-naphthyl radical.  Also called beta-naphthyl group.  the univalent group C 1 0 H 7 –, having a replaceable hydrogen atom in the second, or beta, position; 2-naphthyl group.