Radical bromination of 2 methylbutane

[xstetsonx]

why would radical bromination of 2 methylbutane gives 1-bromo-3-methylbutane, 2-bromo-3-methylbutane, 3-bromo-3-methylbutane, and 1-bromo-2-methylbutane? i don't see any methyl shife in this reaction. Some one please help

 

[chemisttree]

There is no such thing as 3-bromo-3-methyl butane. That's called 2-methyl-2-methyl butane instead.

Draw the structure of 2-methyl butane (it should have 5 carbons). Now brominate each of the primary carbons. When you brominate the primary carbon furthest from the 2-methyl substitution point you change the naming convention to reflect the position of the bromine instead of the methyl since bromine has a higher naming priority than methyl, ie. the 4-position in the starting material becomes the 1-position in the brominated product.