1.4- Dioxane, 2,3-dichloro-, trans

Dichloro-l,4-dioxane, trans- 1,4-Dioxane, 2,3-dichloro-, trans- (3883-43-0), 65, 68... 

It is believed that equatorial substituents such as chlorine or bromine would increase the guest diameter beyond the allowed values (assuming that the guest molecules stack roughly parallel to the canal68)). Support for this comes from the study of fluorocyclohexane where the population of the axial conformer is not enhanced to any major extent70. Nitro-71) and cyano-cyclohexane, trans-l,2-dichloro-, trans-1,2-dibromo-, tram-1,4-dichloro-, trans-1,4-dibromo-, and trans-l-bromo-4-chloro-cyclohexane all pack most efficiently in the thiourea canals as the axial or diaxial conformer 68,72. Tram-2,3-dichloro-1,4-dioxane behaves similarly73. In contrast isocyanato-, tram-1,4-diiodo-, trans-1 -bromo-4-iodo-, and tram-1 -chloro-4-iodo-cyclohexane are present as mixtures of the axial/equatorial or diaxial/diequatorial conformations as appropriate 68,72). The reason for this anomalous behaviour of the iodosubstituted cyclohexanes is not clear. 

Bob Ardrey obtained a first degree in Chemistry from the University of Surrey where he went on to obtain his doctorate stndying the chemistry of trans-2,3-dichloro-l,4-dioxan and the stereochemistry of its reaction prodncts using primarily mass spectrometry and nnclear magnetic resonance spectroscopy. He then carried ont post-doctoral research at King s College, London, into the development of emitters for field-desorption mass spectrometry. 

Compounds in which the carbons are sp3 hybridized display the same confused situation. Erickson 78> reports that the trans vicinal H—H coupling constant of c//-dibromosuccinic anhydride (which is reasonably rigid) varies from 2.5 Hz in CHC13 to 6.0 Hz in acetone and dioxane. The same paper reports that the meso dibromosuccinic anhydride and the two corresponding dichloro compounds do not display any solvent dependence of their coupling constants. (Erickson also reports that lJc.H of the dl- dibromide decreases from 172 Hz in chloroform to 166 Hz in acetone and 165 Hz in dioxane exactly the opposite behavior from that observed for any other 1JC H coupling ever studied). It is at least possible that these data result from chemical degradation of the solute rather than from true solvent effects as discussed here. 

The molecules of trans-2,3- and -2,5-dichloro-l, 4-dioxanes in the crystal are in the chair conformation with both chlorine atoms occupying axial positions (29). In solution, too, there is a preference for this conformation however, the dipole moment for the former molecule in solution is higher than expected for the purely diaxial conformation (30). 

In trans-2,3-di-F- and rrans-2,3-di-Cl-l,4-dioxane, as in the OR analogs, the halogens adopt the diaxial conformation [79NJC145, 79JOC2274 84SPL307]. The corresponding cis isomers, c/s-rrans-2,3,5,6-tetrachloro-, trans-anti-trans-2,3,5,6-tetTachloTO-, 2,2,3,3-tetrachloro-, and 2,2-dichloro-... 

C4H6CI202 trans-2,3-dichloro-1,4-dioxane 3883-43-0 22.14 1.3452 2 3030 C4H605 monoperoxy succinic acid 3504-13-0 25.00 1.3259 2... 

The dipole moment of thietane 1,1-dioxide in benzene solution is 4.49 The dipole moment of 3.33 D for 3-chlorothietane 1,1-dioxide is in better agreement with a planar than a nonplanar ring conformation, The dipole moments of 3-hydroxy-3-methyl-(jU = 4.73 D, dioxane, axial OH), 3,3-dimethyl (jli = 4.56D, CCI4), 3-phenoxy-( u = 4.13 D, CCU), and 2,3-dichloro-4,4-diphenyl (cis, 2a, 3e, /.i = 4.51 D, CeHg trans 2e, 3e, = 3.32 D, thietane 1,1-dioxides have been... 

Dichloro- and -diphenyl-1,4-dioxan The so-called cis 2,3-dichloro-l,4-dioxan, m.p. 52°, is actually the irtms-isomer the 2,3-diphenyl-l,4-dioxans with m.ps. 46° and 132° should be designated cis and trans respectively the dioxan ring has a chair conformation throughout Chen and Le Ffevre, 1965... 

Altona C, Knobler C, Romers C (1963) The conformation of non-aromatic ring compounds. VII. Crystal structure of trans-2,5-dichloro-l,4-dioxane at 125 °C. Acta Cryst 16 1217-1225... 

Halogen atoms in 1,4-dioxane prefer to occupy an axial position, favored by an anomeric effect For this reason, trans-2,3-dichloro-l,4-dioxane prefers the diaxial geometry 1 ... 

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