Predict all the alkenes that would be formed by dehydrohalogenation of the following halides with sodium ethoxide in ethanol and identify the major alkene:
$(i)$ $1-$Bromo$-1-$methylcyclohexane
$(ii)$ $2-$Chloro$-2-$methylbutane
$(iii)$ $2,2,3-$Trimethyl$-3-$bromopentane.

(N/A) $(i)$ In $1-$bromo$-1-$methylcyclohexane,all $\beta$-hydrogen atoms are equivalent. Thus,dehydrohalogenation gives only one alkene: $1-$methylcyclohexene.
$(ii)$ In $2-$chloro$-2-$methylbutane,there are two sets of $\beta$-hydrogens. Dehydrohalogenation yields two alkenes:
$CH_3-C(Cl)(CH_3)-CH_2-CH_3 \xrightarrow{C_2H_5ONa/C_2H_5OH} CH_3-C(CH_3)=CH-CH_3 \text{ (major, } 2-$methylbut$-2-$ene$)$ $+ CH_2=C(CH_3)-CH_2-CH_3 \text{ (minor, } 2-$methylbut$-1-$ene$)$
According to Saytzeff's rule,the more substituted alkene ($2-$methylbut$-2-$ene$)$ is the major product.
$(iii)$ In $2,2,3-$trimethyl$-3-$bromopentane,there are two sets of $\beta$-hydrogens. Dehydrohalogenation yields two alkenes:
$CH_3-C(CH_3)_2-C(Br)(CH_3)-CH_2-CH_3$ $\xrightarrow{C_2H_5ONa/C_2H_5OH} CH_3-C(CH_3)_2-C(CH_3)=CH-CH_3 \text{ (major, } 3,4,4-$trimethylpent$-2-$ene$)$ $+ CH_3-C(CH_3)_2-C(=CH_2)-CH_2-CH_3 \text{ (minor, } 2,3,3-$trimethylpent$-1-$ene$)$
According to Saytzeff's rule,the more substituted alkene ($3,4,4-$trimethylpent$-2-$ene$)$ is the major product.