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(diolefins), unsaturated hydrocarbons having two double bonds. Depending on the mutual positions of the double bonds in the molecule, three types of dienes are distinguished: (1) dienes with isolated bonds, for example, pentadiene-1,4

and other dienes of the type

with chemical properties resembling those of olefins; (2)

dienes with adjacent double bonds Dienes forming

the class of allenes; (3) dienes with conjugated (alternating) double bonds, for example, 1,3-butadiene (divinyl)

2-methyl-butadiene-1,3 (isoprene)


2-chloro-butadiene-1,3 (chloroprene)


and cyclopentadiene

Ordinarily the term “diene” implies compounds with conjugated double bonds. In such compounds, the π bonds are conjugated and a single π-electron cloud is formed, giving rise to an increase in the energy of formation of the molecule, some averaging of the distances between the carbon atoms, the high polarizability of the molecule, and the ability of the molecule to undergo not only ordinary addition reactions at double bonds (1,2-addition), but also addition to the ends of the conjugated system (1,4-addition). Thus a bromine molecule adds to butadiene-1,3 to give 3,4-dibromobutene-l and l,4-dibromobutene-2:

Diene synthesis of the 1,4-addition type. Conjugated dienes (for example, butadiene, isoprene, and chloroprene) readily polymerize and copolymerize forming highly elastic polymers and copolymers. Stereospecific polymerization of isoprene yields a rubber whose structure is identical to that of natural rubber.


References in periodicals archive ?
Among other previously unseen images is a De Dienes shot taken of Monroe when she was 23 in a rare moment, where she was without make-up, the Telegraph reported.
Dienes Corporation is expanding its product offerings to include sales and service of Vorwald air and mechanical shafts in North America.
Dienes Group, Overath, Germany, has founded Dienes France in Samoreau, near Paris, France.
Since the PQAS holder was first developed The Dienes Group has established 9 locations worldwide that now employ over 500 employees.
Dienes Corporation, Spencer, MA has recently made two changes in personnel.
Dienes Werke has introduced the Twin Cut fully automatic slitting system designed to process products, such as paper, film, foil and nonwovens by utilizing a set of identical knives on the top and bottom, which employ non-compression (NC) technology.
Dienes has recently been elected President of United Companies Financial Corporation, a $2 billion nationwide financial services concern (NASDAQ:UCFC).
Dienes Werke has new grinding machines for grinding and polishing all kinds of circular knives, and especially for regrinding the top and bottom knives of slitting machines and sheeters.
Dienes Werke has introduced a new grinding machine, Semi DC-3, for grinding and polishing all kinds of circular knives, especially for regrinding the top and bottom knives of slitting machines and sheeters.
Dienes offers a new German industrial design knife holder with clamping.
The Dienes chord gauge Easy Check provides a quick, simple method for operators to set the proper overlap depth of a male top knife to the female bottom knife.
Dienes has been instrumental in creating a number of complete product lines.