个人认为楼主的化合物存在阻转异构。因为这个化合物6,6'-dimethylbiphenyl-2,2'-diol
有异构,楼主的化合物取代基团更大,也会旋转受阻。
CHIRAL HYDRIDE REAGENTS CONTAINING (R/S)-2,2′-DIHYDROXY-6,6′-DIMETHYLBIPHENYL FOR REDUCTION OF ALKYL PHENYL KETONES
cuturl('http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=cl1972&cdvol=13&noissue=6&startpage=899')
(楼主的化合物跟五味子中联苯双酯类化合物结构有几分相似)
邻位取代的联苯类化合物,由于Ar-Ar单键自由旋转受阻,很容易产生阻转异构现象。当然,这个取代基的大小密切相关。“一般地,当联苯的四个邻位取代基半径之和较大时,则可能存在一对对映体。典型的基团大小顺序为:I>Br>CH3>Cl>NO2>NH2~COOH>OH>F>H 只要两个基团的半径之和大于F和COOH的半径之和,就会使单键旋转受阻,其对映体就会稳定存在。否则,就会发生消旋化。”
a clear picture had emerged of this class of compounds in which Ar-Ar rotation is hindered by steric encumbrance between the ortho substituents W, X, Y and Z. An empirical rule was evident: at least three of W, X, Y and Z must be larger than H for the conformers of 2 to exist as stable enantiomers, and even with this condition satisfied, compounds carrying substituents as small as F or OMe might still not be resolvable.
source: Barriers to rotation about the chiral axis of tertiary aromatic amides
cuturl('http://clor2.ch.man.ac.uk/~jpc-website/downloadable/published%20pdfs/kinetics.pdf')
一篇计算联苯类化合物旋转阻力的文献
Torsional Barriers and Equilibrium Angle of Biphenyl: Reconciling Theory with Experiment
cuturl('http://pubs.acs.org/doi/abs/10.1021/ct800182e')
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本帖最后由 aa_tang 于 2009-3-8 12:53 编辑 ]