Alkane groups

Many molecules of interest to chemistry and biology contain H atoms. For the unimolecular dissociation of the excited states of such molecules, it is instructive to think of elimination of a particle or a group of particles. Thus, we can think of elimination of an electron, an H atom, an H2 molecule, an alkane group (in suitable cases), and so forth. Other factors remaining the same, the rate of the process may... 

Most organic compounds can be derived from alkanes. In addition, many important parts of organic molecules contain one or more alkane groups, minus a hydrogen atom, bonded as substituents onto the basic organic molecule. As a consequence of these factors, the names of many organic compounds are based on alkanes. It is useful to know the names of some of the more common alkanes and substituent groups derived from them, as shown in Table 1.3. 

Some attention has been given to the toxicity of octadecylamine, which contains a straight-chain, 18-carbon alkane group, because of its use as an anticorrosive agent in steam lines. There is some evidence to suggest that the compound is a primary skin sensitizer. 

Figure 15.2 Alkyl polyamines in which two or more amino groups are bonded to an alkane group.

Alkane groups unsubstituted by heteroatoms absorb downfield from TMS to about 60 ppm. (Methane absorbs at 2.5 ppm upfield from TMS.) Within this range we can predict the chemical shifts of individual C atoms in a straight chain or branched chain hydrocarbon from the data in Table 4.1 and the formula S = -2.5 + SnA. 

Nevertheless, thermodynamic reversibility may prove a disadvantage in particular systems. A classic example is provided by the synthesis of individual rotax-anes ( bead on a thread compounds), discussed in detail in Chapter 4. After threading of the macrocyclic bead on to an open-chain component by self-assembly, it has been found desirable to block the reverse (unthreading) pathway by subsequent covalent attachment of branched alkane groups to each end of the thread so that any tendency for separation of the components is blocked. That is, the final covalent step is equivalent to tying a knot in each end of the thread to stop the bead from slipping off. 

The bilayer sheet, also shown in Figure 1,12, is like a sandwich. The "bread" is composed of water-soluble groups and the "filling" of alkane tails. The alkane groups associate with one another but have little contact with the water above and below. 

Recent studies using solid-state NMR reveal that some of the decomposition-resistant polymers n soils may have long-chain alkane groups. 

It is nonspecific and can oxidize several substrates (otherwise difficult to oxidize), e.g., alkanes, alkane groups, or nonsubstituted phenyls. 

Fig. 3.8. (a) a-hexithiophene, an oligomeric form of polythiophene. This material is typically vacuum deposited, (b) Adds two alkane groups at the ends, which improves the material crystallinity [29]. Despite the methyi groups the solubihty in common solvents is low. (c) An oligofluorene with strong seif-organizing properties when deposited on a heated substrate [28]... 

In many studies of wettability Zisman and coworkers have used the contact angles of a series of n-alkanes as a convenient means for determining for low energy solid surfaces [5,6,13,20]. In Figure 2 are plotted the cos 9 vs. 7lv° curves for the n-aUtanes on PMMA surfaces containing 0.5% additive I and 1.0% additive II. The critical surface tensions with additives I and n were 19 and 20 dynes per cm., respectively, representing a decrease of about 20 dynes per cm. from the value of obtained with the additive-free surface. Since the y values of 19 and 20 dynes per cm. are very close to that of 18 dynes per cm. reported by Fox and Zisman [l3] for the n-alkanes on poly-tetrafluoroethylene surfaces, it is apparent that a number of perfluoro-alkane groups are present in the outermost part of the surface phase with the principal axis of each carbon-carbon chain parallel to the surface. 

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