Which of the following chloride will exclusively give 2-methyl but-2-ene on dehydrochlorination by a strong base?
1) 1-chloro-2-methylpropane
2) 2-chloro-2-methylpropane
3) 1-chloro-2,2-dimethylpropane
4) 2-chloro-2,2-dimethylpropane