O-Cyanobiphenyl

A solution of 20 g. (0.12 mole) of o-aminobiphenyl in hydrochloric acid is diazotized in the usual manner [Org. Syntheses Coll. Vol. 1, 170 (1941)], and the solution of the diazonium salt is added to a solution of cuprous cyanide prepared from 35 g. of copper sulfate [Org. Syntheses Coll. Vol. 1, 514 (1941)]. When evolution of nitrogen ceases, the mixture is warmed for 30 minutes on a water bath and then made alkaline with sodium hydroxide. The mixture is steam-distilled, and the distillate is agitated with stannous chloride solution. SuflBcient sodium hydroxide is added to precipitate the tin, and the mixture is extracted with ether. The ethereal solution is dried and distilled to give 11.0 g. (50%) of o-cyanobiphenyl boiling at 174°/13 mm., m.p. 37°. 

D. O., Micro-reactor synthesis synthesis of cyanobiphenyls using a modified Suzuki coupling of an aryl halide and aryl boronic acid, in Ehefeld, W. (Ed.), Microreaction Technology 3rd International Conference on Microreaction Technology, Proc. of... 

By using this method, 4-methyl-2 -cyanobiphenyl, an important intermediate for the synthesis of the antihypertensive drug Losartan, can be easily prepared.132 2-(t>-Chlorophenyl)-oxazoline reacts with excess of arylmagnesium halide without catalysis, as it was shown by Meyers for 2-(o-methoxyphenyl)-oxazolines.133 Cobalt(ll) salts catalyze the coupling of Grignard reagents with a-chloroazines at —40°C in ether (Scheme 47).134 135... 

Fig. 8. The dependence of the nematic-isotropic transition temperature, T i, on the total number of atoms, n, in the spacer for the cyanobiphenyl dimers linked via ether (O) [18], alkyl ( ) [16] and carbonate groups ( ) [16, 53]...

Figure 12. Transition temperatures observed on heating 4-n-alkoxy-4 -cyanobiphenyls [228], poly n-[(4 -(4"-cyanophenyl)phenoxy)alkyl]vinyl ether]s ( ) = 17-32, pdi= 1.09- 1.21) [122- 127, 212, 213], n-[(4 -(4"-cya-nophenyl)phenoxy)alkyl]vinyl ethers [122-127] and a-ethoxy-(u-(4-n-alkoxy-4 -cyanobiphenyl)s [122-127] from the glassy ( ), crystalline (O), SmC ( ), SmA ( ) and nematic (A) states.

FIGURE 7.1 Chemical structures of the main-chain LCs treated in this chapter, nCB being included for comparison. Phase-transition temperatures (DSC) are given to the individual formulas. Note that o, [Pg.286]

The NMR technique has provided useful information regarding the orientational characteristics of nematic liquid crystals [96]. In many examples, the order parameters of the mesogenic core comprising a linear array of aromatic nuclei have been accurately determined from the observed dipolar (Dhd) and quadrupolar (Av) splittings by using deuterium-substituted samples. An attempt was made to elucidate the nematic conformation of the polymethylene-type spacer involved in dimer compounds, o, ct)-bis(4-cyanobiphenyl-4 -yloxy)alkanes (CBA- , with = 9,10), by the combined use of NMR and RIS analysis. The chemical structures and the phase transition data obtained by differential scanning calorimetry (DSC) are shown in... 

At the present time, as shown by the pocket calculator, materials are available with adequate electro-optic performance where the duty cycle is 1 in 2, 3 or 4. Where temperature compensation is used, 1 in 7 duty cycle is possible O with mixtures of cyanobiphenyls and benzoate esters. For a duty cycle of 1 in 10, temperature compensation is a must and the electro-optic performance is determined principally by the threshold sharpness. By way of example. Fig. 36 shows a viewing cone plot for ZLl 1253 (dotted line curves) compared with a sharper threshold material (1.65) (solid line curves) in an 8y, low tilt cell. By single frequency addressing, a 1 in 10 duty cycle is approaching the maximum for an acceptable performance in a twisted nematic display. 

Figure 1 Molecular structures of (A) 4 -(hexyloxy)-4 -cyanobiphenyl (60CB), (B) 2,3-naphthylene bis[2-fluoro-4-(4-dodecyloxybenzoyloxy)benzoate] (N(2,3)-F-012), and (C) 1.3-phenylene bis[4-(4-14-tetradecyloxyphenyl)iminomethyl benzoate] (P10-O-PIMB), with the atomic labeling as used in this chapter.

Figure 5.18 Illustrating odd-even effects for liquid crystals. Data for the a, o)-bis-(4-cyanobiphenyl-4-yloxy)alkane (BCBOw) series of nematogens, plotted as a function of the number of methylene groups in the flexible spacer, n. (o) Variation of the nematic-isotropic transition temperature ( ) variation of the nematic-isotropic phase transition entropy. [Data from J. W. Emsley et aL, Molec. Cryst. Liq. Cryst. Lett., 102, 223 (1984)]...

The alkoxy analogue can be prepared in a variety of ways, one route involves the bromination of protected hydroxybiphenyl, subsequent deprotection and alkylation which results in the creation of the alkoxy bromobiphenyl, see the left-hand side of Fig. 28. Cyanation using copper(I) cyanide as above yields the final product. Alternatively, the alkoxy cyanobiphenyls can be prepared by a cross-coupling procedure as shown on the right-hand side of Fig. 28. Selective coupling of 4-iodo-bromobenzene with an alkoxyphenyl boronic acid in the presence of palladium(O) yields the alkoxy bromobiphenyl. Cynanation proceeds as described previously. 

The two most extensively studied series of liquid crystal dimers are the a,characteristic behavior of dimers. The acronyms used to refer to these series are BCBOn and m.0n0.m, respectively, in which n refers to the number of methylene groups in the flexible spacer and m that in the terminal alkyl chains. The particular interest in these series arises, in part, because they may be considered to be the dimeric analogues of the 4- -alkyloxy-4 -cyanobiphenyls (nOCB) and the N-(4-n-alkyloxybenzylidene)-4 -n-alkylanilines, respectively, which are probably the most widely studied series of conventional low molar mass liquid crystals. In addition, members of the m.OnO.m series were the first dimers for which extensive smectic polymorphism was observed. 

Fig. 3 Effect of the linking group on the odd-even character of the polymethylene-type spacer [ 14]. The latent entropy, A5ni/R, oscillates with the number of methylene units ( ) of the spacer. The three upper curves represent the dimer, and the two lower curves are for the monomer LCs. Filled symbols indicate the carbonate-type dimer, a,o)-bis[(4,4 -cyanobiphenyl) oxycarbonyloxy]alkane (CBC-n filled circles) and the monomer LC, 4 -n-alkoxycarbonyloxy-4-cyanobiphenyl (/lOCCB filled squares). The open symbols indicate the ether-type dimer, a,co-bis[(4,4 -cyanobiphenyl)oxy] alkane (CBA-n open circles), the ester-type dimer, a,o)-bis[(4,4 -cyanobiphenyl)carbonyloxy] alkane (CB-n open triangles), and the ether-type monomer LC, 4 - -alkoxy-4-cyanobiphenyl (nOCB open squares)...

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