- Synthesis and Liquid Crystal Properties of Dimethylene Linked Compounds Incorporating the Cyclobutane or Spiroheptane Rings
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The preparation of sixteen dimethylene linked compounds is described heptane ring>, and a comparison is made between the transition temperatures of these compounds and those of the corresponding esters.This comparison once again highlights the fact that the cyclobutane ring should be regarded, in terms of its ability to promote nematic thermal stability, as a "chain stiffener rather than as a ring system.A comparison is also made of the nematic thermal stabilities of the trans-cyclobutane and the spiroheptane systems and of the trans-cyclohexane and the spiroundecane systems.
- Chan, L. K. M.,Gemmell, P. A.,Gray, G. W.,Lacey, D.,Toyne, K. J.
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p. 229 - 246
(2007/10/02)
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- Synthesis and liquid crystal properties of compounds incorporating cyclobutane, spiroheptane and dispirodecane rings
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A number of esters of structure (I) incorporating the cyclobutane, spiroheptane, or dispirodecane rings has been prepared using a diethyl malonate synthesis.Strict comparison of the liquid crystal behaviour amongst the three classes containing a terminal cyano-substituent was not possible because both the cyclobutanes and dispirodecanes are mixtures of cis- and trans-isomers; the spiroheptanes are racemic systems.Using preparative hplc, it was however possible to isolate the pure cis- and trans-isomers of two of the cyano-substituted cyclobutane esters (I; R = alkyl, -X- = --, Y = CN).From the physical data and the results for the corresponding spiroheptane esters, conclusions regarding the effects of these ring systems on liquid crystal behaviour were obtained.The pure cis- and trans-isomers of the cyclobutane ester (I, R = C3H7, -X- = --, Y = CN) have been assessed for the trends in both order parameter and viscosity with temperature; the results support the idea that idea that the trans-cyclobutane ring adopts a more planar conformation at higher temperatures.Keywords: cyclobutane- and related spiro-systems, cis-/trans-isomerism, order parameter, briefringence, viscosity, structure/property relations.
- Chain, L. K. M.,Gemmel, P. A.,Gray, G. W.,Lacey, D.,Toyne, K. J.
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p. 113 - 140
(2007/10/02)
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- LONG-ACTING CONTRACEPTIVE AGENTS: CYCLOPROPYL AND CYCLOBUTYL ESTERS OF NORETHISTERONE
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Several esters of norethisterone (17α-ethynyl-17β-hydroxyestr-4-en-3-one) with carboxylic acids containing a cyclopropyl or cyclobutyl ring have been synthesized and the stereochemistries of the side-chains determined.
- Shafiee, A.,Vossoghi, M.,Savabi, F.,Vlahov, R.,Tarpanov, V.,et al.
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p. 291 - 308
(2007/10/02)
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