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From Wikipedia


2-Butene is an acyclic alkene with four carbon atoms. It is the simplest alkene to shown cis/trans-isomerism (also known as (E/Z)-isomerism); that is, it exists as two geometrical isomers cis-2-butene ((Z)-2-butene), shown at the right, and trans-2-butene ((E)-2-butene), not shown.

It is a petrochemical, produced by the catalytic cracking of crude oil. Its main uses are in the production of gasoline (petrol) and butadiene, although some 2-butene is also used to produce the solvent butanone via hydration to 2-butanol followed by oxidation.

The two isomers are extremely difficult to separate by distillation because of the proximity of their boiling points (4 °C for cis and 1 °C for trans). The more elongated trans-molecule which has a tougher job to get its tail free from the liquid has the higher boiling point, the more rounded cis isomer escapes easier, thus having a lower boiling piont. However, separation is unnecessary in most industrial settings, as both isomers behave similarly in most of the desired reactions. A typical industrial 2-butene mixture is 70% (Z)-2-butene (cis-isomer) and 30% (E)-2-butene (trans-isomer). Butane and 1-butene are common impurities, present at 1% or more in industrial mixtures, which also contain smaller amounts of isobutene, butadiene and butyne.

From Encyclopedia


alkyne , any of a group of aliphatic hydrocarbons whose molecules contain one or more carbon-carbon triple bonds (see chemical bond ). Alkynes with one triple bond have the general formula C n H 2n-2 . In the International Union of Pure and Applied Chemistry (IUPAC) system of chemical nomenclature, the name of an alkyne is derived from the name of the corresponding alkane by replacing the - ane alkane suffix with - yne and, if necessary, adding a prefix to indicate the location of the triple bond in the molecule. The IUPAC name of the simplest alkyne, HC[triple bond]CH, is thus ethyne, which is derived from ethane. Ethyne is more commonly known as acetylene ; it is an extremely important starting material in commercial chemical synthesis. The next simplest alkyne is propyne, CH 3 C[triple bond]CH. There are two butynes, 1-butyne and 2-butyne, which are structural isomers that differ in the location of the triple bond in their molecule. The alkynes are sometimes referred to as the acetylene series, the higher members of the series being named as derivatives of acetylene, e.g., propyne as methylacetylene, 1-butyne as ethylacetylene, and 2-butyne as dimethylacetylene. The usefulness of the alkynes in chemical synthesis is due both to the reactions of the triple bond itself and to the relative acidity of a hydrogen atom bonded to a triply bonded carbon.

From Yahoo Answers

Question:2. Number of acidic hydrogen atoms present in 1-butyne is (a) 3 (b) 2 (c)1 (d) 4

Answers:1 HCCHCH2CH3 The first hydrogen is an acidic hydrogen

Question:What is the expected major product arising from reaction of 1-butyne with two mole equivalents of Br2? a. 2,2,3,3-tetrabromobutane b. 1,1,2,2-tetrabromobutane c. 1,2-dibromo-1-butene d. 2,3-dibromo-1-butene e. butene

Answers:b.1,1,2,2-tetrabromobutane addition of halogens in alkyne---- chlorine and bromine readily add to alkyne first forming 1,2,-dihaloalkenes and then 1,1,2,2-tetrahaloalkenes and during reaction with bromine the reddish brown colour of br2 is decolourised and hence this reaction is used as a test of unsaturation ......i.e. for double and triple bond....and reactivity order of halogens are cl2>br2>i2... so if you have used one mole than only 1,2-dibromobutene would have been formed...but since there are two moles so 1,1,2,2-tetrabromobutane is formed.........


Answers:3- methyl - 1 butine is CHCCH(CH3)CH3 the condensed formula is C5H8 3,4 - dimethyl- 1 - pentene is CH2=CH C(CH3)2 CH2CH3 the condensed formula is C7 H 14

Question:More specifically butyne from butene?

Answers:Are you referring to 1-butyne and 1-butene? If it is 1-butyne, you can use the Tollen's reagent (ammoniacal silver nitrate) because it is a terminal alkyne. Alkenes and internal alkynes don't react with this reagent .