Straight side chain

Adding a straight side chain lowers knock rating. The effect increases with chain length. 

Change from one straight side chain to two at given molecular weight raises rating. 

Adding a straight side chain to benzene lowers knock rating. The effect increases with chain length. As an exception, ethylbenzene falls below n-propylbenzenc by most methods. 

Gustafsson et al. [73] proposed a model with straight side chains within the planes of the main chains. They found that the orthorhombic unit cells could just accommodate the polymers with short side chains (butyl to hexyl) without interdigitation, whereas longer side chains from neighbouring polymer strands had to interdigitate (place themselves alternately between each other). Gustafsson et al. did not, however, test the model with intensity calculations. 

In their analysis of diffraction data from PDT Bolognesi et al. [79] introduce a coplanar structure with almost straight side chains, but with the molecular planes tilted about 50° with the 6-axis, and with nearest neighbouring main chains being shifted along the chain direction by c/2 relative to each other. This model was claimed to give reasonably good fit between calculated and observed intensities. 

PDT has been studied also by the Cracow group [59,81 83]. In a recent work by Luzny [83] computer modelling was performed, based upon straight side chains, but allowing for C—C bond twists between... 

Fig. 15 New type of PFSA with straight side chains...

In addition to these main-chain liquid crystalline polymers, there are also side-chain liquid crystalline polymers, where the liquid crystalline nature arises from the presence of rigid straight side-chain units (called the mesogens) chemically linked to an existing polymer backbone either directly or via flexible spacer units. 

Hammen equation A correlation between the structure and reactivity in the side chain derivatives of aromatic compounds. Its derivation follows from many comparisons between rate constants for various reactions and the equilibrium constants for other reactions, or other functions of molecules which can be measured (e g. the i.r. carbonyl group stretching frequency). For example the dissociation constants of a series of para substituted (O2N —, MeO —, Cl —, etc.) benzoic acids correlate with the rate constant k for the alkaline hydrolysis of para substituted benzyl chlorides. If log Kq is plotted against log k, the data fall on a straight line. Similar results are obtained for meta substituted derivatives but not for orthosubstituted derivatives. 

Coniine (12), impHcated by Plato in the death of Socrates, is the major toxic constituent of Conium maculatum L. (poison hemlock) and, as pointed out eadier, was apparendy the first alkaloid to be synthesized. For years it was thought that coniine was derived from lysine (24), as were many of its obvious relatives containing reduced piperidine nuclei and a side chain, eg, peUetierine (46). However, it is now known (99) that coniine is derived from a polyketooctanoic acid [7028-40-2] (138), CgH QO, or some other similar straight chain analogue. 

StmcturaHy, guar gum comprises a straight chain of D-mannose with a D-galactose side chain on approximately every other mannose unit the ratio of mannose to galactose is 2 1 (53). Guar gum has a molecular weight on the order of 220,000 (54). 

As shown in Table 3, the glass-transition temperatures of the amorphous straight-chain alkyl vinyl ether homopolymers decrease with increasing length of the side chain. Also, the melting points of the semicrystalline poly(alkyl vinyl ether)s increase with increasing side-chain branching. 

Although the biosynthetic cascade hypothesis predicts the co-occurrence of endiandric acids D (4) and A (1) in nature, the former compound was not isolated until after its total synthesis was completed in the laboratory (see Scheme 6). Our journey to endiandric acid D (4) commences with the desilylation of key intermediate 22 to give alcohol 31 in 95% yield. The endo side chain is then converted to a methyl ester by hydrolysis of the nitrile to the corresponding acid with basic hydrogen peroxide, followed by esterification with diazomethane to afford intermediate 32 in 92% overall yield. The exo side chain is then constructed by sequential bromination, cyanide displacement, ester hydrolysis (33), reduction, and olefination (4) in a straight-... 

For the most part, the corrosion protection potential of filmers improves with increased packing of amines onto the metal surface, so straight-chain-only amines are preferred (no side chains or branched-chain amines) for formulation purposes. 

The names of straight-chain alkanes are given in Table 18.1 they all end in -ane. Name a hydrocarbon side chain as a substituent by changing the ending -ane to -yl (as in the last two columns in Table 18.1). 

The Hammett equation is the best-known and most widely studied of the various linear free energy relations for correlating reaction rate and equilibrium constant data. It was first proposed to correlate the rate constants and equilibrium constants for the side chain reactions of para and meta substituted benzene derivatives. Hammett (37-39) noted that for a large number of reactions of these compounds plots of log k (or log K) for one reaction versus log k (or log K) for a second reaction of the corresponding member of a series of such derivatives was reasonably linear. Figure 7.5 is a plot of this type involving the ionization constants for phenylacetic acid derivatives and for benzoic acid derivatives. The point labeled p-Cl has for its ordinate log Ka for p-chlorophenylacetic acid and for its abscissa log Ka for p-chloroben-zoic acid. The points approximate a straight line, which can be expressed as... 

Figure 6.8 Phthalocyanine 63 self-assembles in chloroform to give bundles of micrometer length fibers. Single fibers have diameter of 50 A (highlighted between arrows) and can be envisaged as nanowires (top left). Chiral derivative 64 forms left-handed super helices (top right) due to chirality within side chains. This chiral expression can be turned-off by addition of K+ ions, which bind within the crown-ether part of the molecule, forcing the phthalocyanines to be stacked directly on top of each other, resulting in straight wires (bottom left).

This section on the contraction factor may be concluded with an example of a comb macromolecule [136]. Due to the route of preparing this comb, unattached side chains also occurred in the system. Figure 27 shows the result of the molar mass dependence of [rj] which was obtained from a SEC/LALLS/VISC fractionation. One observes at low molar masses a straight line with an exponent of 11 =0 JO that coincides with the exponents of linear side chains. It follows a... 

It must be noted that the end-to-end distance of the brushes is also affected by adsorbing them flatly on a hard wall. In monolayers (d = 2) the molecules are constrained to two dimensions which favors extension and parallel aUgnment [ 163 ]. This is particularly pronounced if the side chains get tightly adsorbed and will be discussed in detail below. Yet even in the case of a weak interaction with a substrate, the chains are extended. In contrast, in thick films the individual chain can adopt a less straight conformation by transition between layers in the z-direction. Figure 24 clearly demonstrates the difference in the ordering of cylindrical brushes of polystyrene depending on the film thickness [78]. 

Silk is produced from the spun threads from silkworms (the larvae of the moth Bombyx mori and related species). The main protein in silk, fibroin, consists of antiparallel pleated sheet structures arranged one on top of the other in numerous layers (1). Since the amino acid side chains in pleated sheets point either straight up or straight down (see p. 68), only compact side chains fit between the layers. In fact, more than 80% of fibroin consists of glycine, alanine, and serine, the three amino acids with the shortest side chains. A typical repetitive amino acid sequence is (Gly-Ala-Gly-Ala-Gly-Ser). The individual pleated sheet layers in fibroin are found to lie alternately 0.35 nm and 0.57 nm apart. In the first case, only glycine residues (R = H) are opposed to one another. The slightly greater distance of 0.57 nm results from repulsion forces between the side chains of alanine and serine residues (2). 

---