1- Chloro-2-methyl-l-butene

Bromination of isoprene using Br2 at —5 ° C in chloroform yields only /n j -l,4-dibromo-2-methyl-2-butene (59). Dry hydrogen chloride reacts with one-third excess of isoprene at —15 ° C to form the 1,2-addition product, 2-chloro-2-methyl-3-butene (60). When an equimolar amount of HCl is used, the principal product is the 1,4-addition product, l-chloro-3-methyl-2-butene (61). The mechanism of addition is essentially all 1,2 with a subsequent isomerization step which is catalyzed by HCl and is responsible for the formation of the 1,4-product (60). The 3,4-product, 3-bromo-2-methyl-1-butene, is obtained by the reaction of isoprene with 50% HBr in the presence of cuprous bromide (59). Isoprene reacts with the reactive halogen of 3-chlorocyclopentene (62). 

The sfflne two alcohols are formed in the hydrolysis of l-chloro-3-methyl-2-butene ... 

The carbocation formed on ionization of l-chloro-3-methyl-2-butene is the same allylic carbocation as the one formed on ionization of 3-chloro-3-methyl-l-butene and gives the same mixture of products. 

In contrast to the above case, addition of HCl to 1,1-dimethylallene at —78°C gives at least two thirds and possibly exclusively l-chloro-3-methyl-2-butene, 33, although these results are complicated by rearrangement of the allene to isoprene and the addition of HCl to the isoprene (65). No satisfactory explanation was offered (65) and none is readily available within the carbonium framework to account for the unusual orientation in this addition. Certainly the tertiary carbonium ion, 34, should be more stable than the primary carbonium ion, 35, since neither is stabilized by the adjacent perpendicular n center. This result is all the more surprising since tetramethylallene, 36, behaves as expected... 

Tributyltin chloride Stannane, tributylchloro- (8,9) (1461-22-9) l-Chloro-3-methyl-2-butene 2-Butene, 1 -chloro-3-methyl- (8,9) (503-60-6)... 

The kinetics of the S11CI4-catalysed addition of l-chloro-3-methyl-2-butene or (E)-2-chloro-3-pentene to isoalkenes (e.g. Me2C=CHCH2CH2CMeClPr) have been shown to be strongly influenced by steric effects387. 

One of the most intriguing newly discovered natural organohalogens is l-chloro-3-methyl-2-butene (9) from a secretion of a male flying fox (Pteropus giganteus) (380). Since this compound is known to be a powerful lachrymator (personal experience), it may function as a chemical defensive agent ( allomone ) for the fox. 

The C—X reduction potentials of allylic halides and unsaturated a-haloesters are similar, and vary depending on their substitution pattern. The regioselectivity of the addition, therefore, is also influenced by the relative reduction potentials. l-Chloro-3-methyl-2-butene (41) reacts with diethyl fumarate (42) through attack from the primary carbon (equation 31), whereas with methyl crotonate (44) allylation takes place at the more highly substituted tertiary carbon (equation 32). 

The reduction potential of l-chloro-3-methyl-2-butene (41) is more positive than that of methyl crotonate which results in the initial 2-electron reduction of the allyl halide to give the allyl ion. This species subsequently undergoes Michael reaction through the tertiary... 

Problem 8.10 Account for the fact that 2>methyM,3-butadiene reacts (a) with HCI to yield only 3-chloro-3-mcthyl-l-butcne and l-chloro-3-methyl-2-butene ... 

When 2-methyl-1,3-butadiene (isoprene) undergoes a 1,4-addition of hydrogen chloride, the major product that is formed is l-chloro-3-methyl-2-butene. Little or no l-chloro-2-methyl-2-butene is formed. How can you explain this ... 

Treating either l-chloro-3-methyl-2-butene or 3-chloro-3-methyl-l-butene with Aq20 in water gives (in addition to AgCI) the following mixture of alcohol products. 

Also obtained by reaction of l-chloro-3-methyl-2-butene with phloroisobutyrophenone in the presence of magnesium oxide and potassium iodide in refluxing acetone [8070] under nitrogen or argon [8071],... 

We observe the same effect in the reaction of l-chloro-3-methyl-2-butene in water. Once again, the major product arises by reaction of water with the tertiary carbon of the allyhc carbocation. 

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