Ring substituents, hydrocarbon cores

It would appear that most of the benzene ring structures in humic substances have two or more substituents, such as carbonyl, carboxyl, hydrocarbon, hydroxyl, and methoxyl and other ether functional groups. The evidence from identification of the products of degradation reactions, and more recently from NMR data, suggests that aliphatic hydrocarbons and aliphatic and aromatic ether groups link the core components in the macromolecules, and that carbonyl, carboxyl, and hydroxyl substituents are likely to be attached to some of the aliphatic hydrocarbons (Hayes and Swift, 1978). 

Cyclic hydrocarbons with six equivalent substituent chains emanating from several carbon atoms about the ring can again adopt conformations in which the molecular shape is disk-like, but the aspect ratio is much larger. If the chains are somewhat flexible and the molecules possess an appropriate balance between order and disorder and attractive and repulsive intermolecular forces, the creation of new mesophase types can be envisioned - and several have been found [102,104]. The two general classes of aggregation in liquid crystalline phases of discotic molecules are lenticular nematic (N ) and columnar discotic (D) [100-104]. Carbonaceous pitch mesophases, discussed in section 1.4.5, resemble phases. Only those discotic mesophases with benzene, cyclohexane and shape-related cores having primarily alkyl chains as substituents will be discussed here. 

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