Note 858

The range of molecular compounds, MC, is utterly rich, and the possibility-in-principle to generate them is almost everywhere to be found.
If unification between several already saturated-as-to-chief-valences identical molecules into higher organized independent particles of molecular size takes place, one speaks of "association", in the case of unequal molecules one speaks of "aggregation".
[Here, in this note, and in the main text, we are dealing with how to evaluate the phenomenon of "molecular compounds" in the context of Unimol. A molecular compound must be distinguished from a true chemical compound, an atomic compound, such :  In true molecules, atomic compounds, the chemical parts, conceived in isolation, are atoms or chemical groups that still have left free chief (i.e. true) valences, unsaturated valences. But as soon as they are considered as having chemically taken up into a molecule, i.e. now conceived as parts of a molecule, all their valences are in fact saturated. In molecular compounds, on the other hand, this is not so. There, the chemical groups, the "molecules", making up the molecular compound (MC), the "super-molecule", are not only saturated as to their chief, i.e. true, valences before their unification (as in many chemical reactions) into the super-molecule, but remain so saturated when constituting the super-molecule, the molecular compound, so their type of bonding is quite different at least from a covalent bond.]
The formation of a molecular compound (MC) can chiefly be reduced to the dipolar or multipolar nature of the components (and thus to inter-molecular or adjunct-valence forces). In addition to inter-molecular super-molecule formation, there may be intra-molecular association (Compare maleine acid with the association of both COOH groups [both at the same side of the chain or "axis", both pointing in the same direction], and fumaric acid in which this is not so [both COOH groups pointing in opposite directions]. Consequence :  strong difference in heat-of-evaporation.). Maleine acid and fumaric acid are isomerous (same composition, different structure) acids, in this case, respectively, cis- and trans-isomers :
A measure of the degree of [bond-]strength in MC is the "bond"- or better association-energy, which can be determined as heat-after-mixing of the reaction A + B ==> AB.  The counter-value, and thus the separation-energy, may always statistically easily be produced again, so that most often already a  light  shaking already results in a breakdown.
If, in the interaction between dipoles and polarizable molecules (one speaks also of association complexes), there is a strong mutual influence on the electronic systems [electron clouds], then we have the special case of deformation complexes, forming a "transition" to chemical compounds. The qualitative possibilities [opportunities] inherent in the super-molecular aggregation, to which also applies a law of multiple proportions, are definitely limited, and in themselves -- one has, while ignoring an alleged vitalistic steering agent, to derive a possible appearance of special features from such interactions -- show not a spark of that far-reaching multiplicity as it occurs and is needed in the organismic [i.e. in organisms]. The so-called emergence of new qualities or features  in  and  as  MC masks the fact that the components themselves become impoverished as to qualities, that they [the components] become more stable, less inclined to react, in a lesser degree transformable and "active", that they more than before become ossified. Now one might say :  true chemical bondings carry things still further. This is right, when one has in mind certain  most general  features which, in the present context, are immaterial.  Special  new features emerge in new substances, and thus  after  chemical bonding is established. One should compare the fact that the type "protein" [and thus a general feature] is already indicated by the single amino acid, that it is completely represented by macropolypeptides, very well represented by oligopeptides [i.e. consisting of only a small number of amino acid residues], and satisfactorily already by a tri- or tetra-peptide, whereas the tri- or tetra-merous condition in the [one single] free amino acid, i.e. its associational [identical parts, intra-molecularly] MC, or also its aggregational [different parts, intra-molecularly] MC, stands further away from the protein type than does the monomer [i.e. amino acid without intra-molecular repeating units (equal or different)].
[As an example of, say, a tri-merous amino acid -- not to be confused with a chain of amino acid residues connected to each other by the peptide bond -- may be the coupling of several molecules of the amino acid cysteine through the S-bridge, as we had it ABOVE with two such molecules forming cystine.]  [So it is the general features (such as "protein type") that in true MC (molecular compounds) quickly appear new, while they do not so in true new molecules originated by truly intra-molecular addition.]

Recently, one has pointed to yet another type of association, the so to say histological association. "In the domain of minerals, as also in the animal and plant kingdom, a whole series of solid two-component systems is known :  The fibrous molecules of a substance A, mostly a polyelectrolyte, are ordered parallel to one another and fixed by chemical bonding. In this spatial network as matrix a second substance, B, is deposited such that its crystals with their longer parameter are aligned with the structural direction inherent and pre-existing in the matrix. An example of such a system is the pearl, made up of conchyoline and aragonite" (cited from a 1957 source). Here it is, of course, a clear case of non-living substance. [but it also occurs in living systems :] In the case of vertebrate bones this [non-living state] is already essentially different, because here there is a species of Ca-salt of semi-vital nature, possessing true transitions to genuine living substance. [So, apart from molecular compounds, intra-molecular associations, and hydration, there exist, in the organismic, also this described type of association.].

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