Butyl bromide 2-methylpropene

Methylpropene tert-Butyl bromide Isobutyl bromide... 

The reaction of HBr with 2-methylpropene produces only tert-butyl bromide. 

Addition of HBr to 2-methylpropene gives mainly tert-butyl bromide, because the product with the more stable carbocation intermediate always predominates in this type of reaction. 

The El reaction involves the formation of a planar carbocation intermediate. Therefore, both syn and anti elimination can occur. If an elimination reaction removes two substituents from the same side of the C—C bond, the reaction is called a syn elimination. When the substituents are removed from opposite sides of the C—C bond, the reaction is called an anti elimination. Thus, depending on the substrates El reaction forms a mixture of cis (Z) and trans (E) products. For example, tert-hutyl bromide (3° alkyl halide) reacts with water to form 2-methylpropene, following an El mechanism. The reaction requires a good ionizing solvent and a weak base. When the carbocation is formed, SnI and El processes compete with each other, and often mixtures of elimination and substitution products occur. The reaction of t-butyl bromide and ethanol gives major product via El and minor product via SnI-... 

The reaction of ethoxide ion with tort-butyl bromide in ethanol as solvent results in the formation of the elimination product 2-methylpropene. 

The reaction of tert-butyl bromide with ethoxide ion, shown at the beginning of Section 9.2, resulted in the formation of 2-methylpropene in an E2 reaction. If ethoxide ion is not present in the reaction, E2 elimination is greatly slowed, and both substitution and elimination products are formed. 

Addition of HX to an unsymmetrical alkene could, in principle, give two different products. The ionic reaction between hydrogen bromide (HBr) and 2-methylpropene (isobutylene [(CH3)2CH=CH2]), where both l-bromo-2-methylpropane (isobutyl bromide [BrCH2CH(CH3)2]) and 2-bromo-2-methylpropane (r-butyl bromide [(CH3)3CBr]) could have formed is shown in Equation 6.26. 

Chapter 5 will describe elimination reactions and their mechanisms. In one example, heating tert-butyl bromide in ethanol gives the alkene 2-methylpropene by a two-step mechanism ... 

The product (benzyl f-butyl ether) is primary on the benzyl side and tertiary on the t-butyl side. So, an SN2 type displacement by potassium f-butoxide of benzyl bromide is one approach, and an acid-catalyzed (SN1) process of benzyl alcohol with isobutylene (2-methylpropene) is another method ... 

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