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16, 111* 42* Tetrazole H N-Ns CH N-Structural Formula for Tetrazole npETRAZOLE can be recrystallized from ethyl acetate and other common organic solvents, but the best crystals for both optical and x-ray studies are obtained by slow sublimation (at about 50°C .) onto a microscope slide. Characteristic crystals by sublimation are shown in Figure 1; crystals grown from the melt are shown in Figure 2. An orthographic projection of a typical crystal of tetrazole is shown in Figure 3. All crystal interfacial

This work was undertaken in order to develop a rapid method of identification of small quantities of polynuclear aromatics such as might be obtained as

Morphology in the broad sense being considered here can be taken to include a wide range of characteristics, extending in size from the external shape of large objects to dimensions of the crystal lattice. Many examples can be found which demonstrate the effects of this spectrum of morphological features on a material's physical properties. As examples of the extremes just cited, one can alter the flexural characteristics of formed polymeric objects by altering their shape. Flexural characteristics of some polymers can also be modified by altering their degree of crystallinity. Morphological considerations on the crystal lattice scale relating to effects on physical properties of polymers have received increasing attention in recent years, particularly with the advent of stereoregular polymers. Less is known of the influence of this submicroscopic morphology on chemical reactions. This discussion will deal with some aspects of submicroscopic morphology on a particular type of chemical reaction; namely, polymerization in the solid state. Following a few general considerations, data will be presented to illustrate some specific influences of the crystal lattice on polymerization in the solid state.In considering polymerization in the solid state it is apparent that two general factors are involved: (1) the chemical constitution of the monomer, and (,??) its crystal lattice. Although the minimum chemical requirement for polymerization to occur is easy to specify (the monomer must have an appropriate functional group) , even the minimum crystallographic criteria are not clear in absolute terms. However, some of the morphological factors which can be expected to exert an influence on solid state polymerization behavior are the following.(1) The spatial arrangement of active groups of the monomer in the crystal lattice-their distance apart, and their relative orientation.Molecular mobility is vastly more restricted in the solid state compared to that in the melt or solution, and so for at least the initiation of polymerization, the molecules must be "within reach" of each other. Once polymerization is initiated, the same factors may then influence the reaction rates, and conceivably also the structure (morphology) of the resulting polymer.105