The geometric isomers of 2-butene are also an interesting case. The two isomers of 2-butene are as follows:

Like n-butane, they are too large to form hydrates on their own; however, in a mixture with methane, hydrates do form, but the trans isomer behaves like n-butane, inasmuch as it will enter the hydrate lattice in the presence of hydrate former. On the other hand, the cis isomer is too large to enter the hydrate lattice. Mixtures of methane + trans-2-butene form a Type II hydrate, with the trans-2-butene entering the large cages of the Type II lattice. Mixtures of methane + cis-2-butene form a Type I hydrate because this isomer is not capable of entering the lattice. For evidence of this behavior, see Holder and Kamath (1984).