Butane three-dimensional model

Butane and pentane are examples of alkanes that are sometimes called straight-chain alkanes. One glance at three-dimensional models, however, shows that because of their tetrahedral carbon atoms the chains are zigza ed and not at all straight. Indeed,... 

Three-dimensional models of ethane, propane, and butane. The ball-and-stick models at the left show the way in which the atoms are connected and depict the correct bond angles. The spacefilling models at the right are constructed to scale and give a better idea of the molecular shape, though some of the hydrogens may appear hidden. 

Note that structural formulas are generally not three-dimensional representations of the molecule— as space-filling or ball-and-stick models are— bnt rather two-dimensional representations that show how atoms are bonded together. As snch, the most important feature of a structural formula is the connectivity of the atoms, not the exact way the formula is drawn. For example, consider the two condensed structural formulas for butane and the corresponding space-filling models below them ... 

Increasing the length of the alkyl spacer in such a way as to yield 1,4-bis(tetrazol-l-yl)butane (abbreviated as btzb) (Fig. 16), changes the dimensionality of the Fe(II) spin crossover material [89]. In fact, [Fe(btzb)3] (C104)2 is the first highly thermochromic Fe(II) spin crossover material with a supramolecular catenane structure consisting of three interlocked 3-D networks [89]. Unfortunately, only a tentative model of the 3-D structure of [Fe(btzb)3](Cl04)2 could be determined based on the x-ray data collected at 150 K (Fig. 20). 

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