butyl

In by Mark Goodman

A type of non-curing and non-skinning sealant made from butylene usually used for internal applications.

Merriam-Webster Online Dictionary
butyl (noun)
any of four isomeric alkyl radicals CH− derived from butane - 4 9
butyl (Wikipedia)

In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula −C4H9, derived from either of the two isomers of butane.

The isomer n-butane can connect in two ways, giving rise to two "-butyl" groups:

  • If it connects at one of the two terminal carbon atoms, it is normal butyl or n-butyl: CH3−CH2−CH2−CH2− (fully systematic name: butyl)
  • If it connects at one of the non-terminal (internal) carbon atoms, it is secondary butyl or sec-butyl: CH3−CH2−CH(CH3)− (fully systematic name: 1-methylpropyl)

The second isomer of butane, isobutane, can also connect in two ways, giving rise to two additional groups:

  • If it connects at one of the three terminal carbons, it is isobutyl: (CH3)2CH−CH2− (fully systematic name: 2-methylpropyl)
  • If it connects at the central carbon, it is tertiary butyl, tert-butyl or t-butyl: (CH3)3C− (fully systematic name: 1,1-dimethylethyl)
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