Who knows butyl?

Butyl is a hydrocarbon radical, C4H9, with the structure of butane and valence 1.
　　Ｈ　Ｈ　Ｈ　Ｈ
　　｜　｜　｜　｜
Ｈ－Ｃ－Ｃ－Ｃ－Ｃ－　　ｅｔｃ
　　｜　｜　｜　｜
　　Ｈ　Ｈ　Ｈ　Ｈ
Each of the two isomers of butane give rise to two isomers of the butyl substituent. Thus, n-butane can connect at either the terminal or an internal carbon atoms, giving rise to "n-butyl" and "sec-butyl" substituents.
n-butyl group; CH3CH2CH2CH2–, (fully systematic name "butyl")
sec-butyl group; CH3CH2(CH3)CH–, (fully systematic name "1-methylpropyl")
The second, branched isomer of butane, isobutane can also connect either terminal methyl or internal carbon atoms, giving rise to "isobutyl" and "tertiary butyl" substituents, respectively.
isobutyl group; (CH3)2CHCH2–, (fully systematic name "2-methylpropyl")
tert-butyl group; (CH3)3C–, (fully systematic name "1,1-dimethylethyl")
I hope this can help with your understanding. =)

2007-12-09 20:22:15 補充：
Do butyl rubber be the product you are looking for?Butyl rubber—also known as polyisobutylene and PIB (C4H8)n is a synthetic rubber, a homopolymer of 2-methyl-1-propene. Polyisobutylene is produced by polymerization of about 98% of isobutylene with about 2% of isoprene.

2007-12-09 20:22:36 補充：
Structurally, polyisobutylene resembles polypropylene, having two methyl groups substituted on every other carbon atom. It has excellent impermeability, and the long polyisobutylene segments of its polymer chains give it good flex properties.

2007-12-09 20:22:55 補充：
It can be made from the monomer isobutylene or CH2=C(CH3)2 via radical polymerization, cationic addition polymerization & anionic addition polymerization routes.A synthetic rubber, or elastomer, polyisobutylene is impermeable to air and used in many applications requiring an airtight rubber.

2007-12-09 20:23:30 補充：
Polyisobutylene is used in making adhesives, agricultural chemicals, fiber optic compounds, caulks and sealants, cling film, electrical fluids, lubricants (2 cycle engine oil), paper and pulp, personal care products, pigment concentrates, for rubber and polymer modification,

2007-12-09 20:23:47 補充：
as a gasoline/diesel fuel additive, and even in chewing gum.The first major application of butyl rubber was tire inner tubes. This remains an important segment of its market even today.

butyl is but yl (but you long)