???Thiourea (H2NCSNH2) forms tubular clathrates that are similar in structure to those formed by urea. Combining a mixture of hexadecane and 2,2,4-trimethylpentane with thiourea produces a crystalline solid that decomposes in water to yield 2,2,4-trimethylpentane, but no hexadecane. What is an explanation for this result?

The structure of thiourea  is similar to that of urea.It behaves as monoacidic base and like urea ,forms channel complexes .However ,in this case , the diameter of the channel is about 7A ,and so can accommodate larger molecules  like -2,2,4-trimethylpentane .Apparently the cross section area of straight chain alkanes is too small to support the channels in thiourea and consequently these compounds do not form channel complexes .Here hexadecane is not the part of the tubular clatharates and hence does not come out when the crystalline solid is hydrolyzed.