Face Selectivity of Reactivity

The craters on the (100) face and thus the anisotropic molecular migrations can be measured at up to 2 mm distance from the acid polycrystal. 

Further prominent examples for face selective reactivity (but for different reasons) are encountered with sulfanilic acid monohydrate 16 and 4-aminobenzoic acid 7. They do not diazotize on their (010) face with N02 or on the (001) face with NOC1, respectively, where molecules cannot exit due to infinite hydrogen-bonded strings. Conversely, at slopes on (010) of 16 or on (100) of 7, where the hydrogen-bonded amino groups of the strings are freely available, reaction occurs [18, 32, 33]. 

The reaction of carboxylic acids and phenols with ammonia and amines was studied by Curtin, Paul, Miller, and coworkers using X-ray data, light microscopy, and solid-state NMR [34, 35], They found anisotropic behavior under the light microscope, but frequently could not correlate to what they tried to predict on the basis of topochemistry. The discussion of that failure was postponed and not 

Some of the Important Failures ofTopochemistry and Their Remedy by the Experimental Mechanism 

The crystal packing analysis clearly shows, that there is nothing special with these examples. Anthracene 14 has a layered structure with a (100) cleavage plane 

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