Zigzag format

Bond-line drawings show the carbon skeleton (the connections of all the carbon atoms that build up the backbone, or skeleton, of the molecule) with any functional groups that are attached, such as - OH or -Br. Lines are drawn in a zigzag format, where each comer or endpoint represents a carbon atom. For example, the following compound has 7 carbon atoms ... 

Don t forget that carbon atoms in a straight chain are drawn in a zigzag format ... 

For polymeric chains from tt-sequences, analysis of PACS-4 structure, carried out on Stewart - Briegleb models, indicates a tendency of plane zigzag formation by the siloxane backbone, formed from intercyclic oxygen atoms [43], Evidently, PACS-4 may be approximated by cylinders, diame-ters of which increase with the volume of alkyl substituting agent. Interchain distance, di, indicated by X-ray diffraction data, varies from 8.4 (PMCS-4) to 10.4 A (PECS- 4). Figure 4 shows a hypo-thetical model of POCS-4. 

In contrast to the zigzag formation of linear hydrocarbons, long perfluoroalkyl chains are helical, rigid and rod-like structures [49, 52]. This structure, due to the steric repulsion between fluorine atoms, consists of a full helical twist every 13 carbon atoms [49,52]. Short... 

Rickrack rik- rak [reduplication of rack] (1884) n. Flat braid in zigzag formation. It is produced by applying different tensions to individual threads during manufacture. 

Notice that triple bonds are drawn in a linear fashion rather than in a zigzag format, because triple bonds involve s -hybridized carbon atoms, which have linear geometiy (Section 1.9). The two carbon atoms of a triple bond and the two carbon atoms connected to them are drawn in a straight line. All other bonds are drawn in a zigzag format for example, the following compound has eight carbon atoms. 

Draw in zigzag format, keeping triple bonds linear. 

The crystal structure of many compounds is dominated by the effect of H bonds, and numerous examples will emerge in ensuing chapters. Ice (p. 624) is perhaps the classic example, but the layer lattice structure of B(OH)3 (p. 203) and the striking difference between the a- and 6-forms of oxalic and other dicarboxylic acids is notable (Fig. 3.9). The more subtle distortions that lead to ferroelectric phenomena in KH2PO4 and other crystals have already been noted (p. 57). Hydrogen bonds between fluorine atoms result in the formation of infinite zigzag chains in crystalline hydrogen fluoride... 

The oxide (p. 1209), chalcogenides (p. 1210) and halides (p. 1211) have already been described. Of them, the only ionic compound is HgF2 but other compounds in which there is appreciable charge separation are the hydrated salts of strong oxoacids, e.g. the nitrate, perchlorate, and sulfate. In aqueous solution such salts are extensively hydrolysed (HgO is only very weakly basic) and they require acidification to prevent the formation of polynuclear hydroxo-bridged species or the precipitation of basic salts such as Hg(OH)(N03) which contains infinite zigzag chains ... 

M(0H)2SOi, H2O where M=Zr (8), Hf (12) also have been determined and reveal the presence of almost planar zigzag chains of metal atoms joined by double hydroxide bridges. The single exception to this trend toward formation of double hydroxy-bridged metal dimers or chains is the compound which is best described as CeOSOif,H20 (17). However, even in this structure the cerium ions form chains which are linked by bridging oxide ions. 

With decreasing My B ratio, two or three B zigzag chains are connected at bonding distances, thus forming double or triple chains (Fig. 1). This tendency toward two-dimensional boron net formation (i.e., AlBj type) is recognized from the structural series within the V-B system VnB +, = (n - 1) VB -I- VBj (n = 1,2,3,5 not known for n = 4). ... 

Thus the formation of tilted analogues of the smectic A phases, i.e. monolayer Cl and bilayer C2, is possible for mesogens with relatively large electric quadrupoles. In the case of strongly sterically asymmetric molecules (e.g., zigzag shaped or dumbell shaped molecules, Fig. 3b) these quadrupolar interactions may be steric in origin. From this point of view observation of molecular tilt in the molecular dynamics simulations for a one-layer film of DOBAMBC in the absence of electrostatic interactions is not so surprising [106]. 

From the viewpoint of synthetic polymer chemistry, although the formation of stereospecific polymers (isotactic and syndiotactic) is very popular, the present polymer is the first example having a double syndiotactic structure. In ad tion, the polymer consists of an alternating zigzag-linear main chain structure. 

The complex formation of a-CD with POx was found to obey the same stoichiometry as that for PEG. In fact, the X-ray powder pattern of the complex does not differ from that of the a-CD-PEG complex. Fig. 17(a) illustrates the POx chain in the complex with a-CD when its conformation is planar zigzag, and Fig. 17(b) sketches the POx chain in the / -CD cavity where it favors the T3G conformation thanks to the wider cavity of this CD. 

Fig. 12 Displacement of M atom positions in MnP-type structure relative to NiAs-type structure, with formation of zigzag chains of M-M bonds...

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