The major product of the elimination reaction between 2-chlorobutane and potassium ethoxide in ethanol solvent is 2-butene. This reaction follows the E2 mechanism, where the ethoxide ion acts as a strong base and removes a -hydrogen from the 2-chlorobutane, leading to the formation of a double bond between the and carbons. The chloride ion leaves as a leaving group. The reaction favors the formation of the more substituted alkene, which in this case is 2-butene.