title: A sterically congested cis-stilbene and its phosphonium salt precursor.
abstract: Triphenyl(2,4,5-trimethoxybenzyl)phosphonium chloride is formed in solvent-free form by the reaction under anhydrous conditions between triphenylphosphane and 2,4,5-trimethoxybenzyl chloride, but when it is crystallized from a mixture of ethyl acetate and chloroform in the presence of air it forms a stoichiometric monohydrate, C28H28O3P(+)·Cl(-)·H2O, (I). The reactions between the anhydrous phosphonium salt and alkoxy-substituted benzaldehydes, using Wittig reactions in the presence of potassium tert-butoxide, provide a series of multiply substituted stilbenes, most of which were assigned the Z configuration on the basis of their NMR spectra. However, no such deduction could be made for the symmetrically substituted (Z)-2,2',4,4',5,5'-hexamethoxystilbene, C20H24O6, (II). Compound (II) does in fact have the Z configuration and the molecular geometry provides evidence for steric congestion around the central double bond; in particular, the central alkene fragment is nonplanar, with a C-C=C-C torsion angle of 7.8 (4)°. In hydrated salt (I), the chloride anions and water molecules are linked by O-H···Cl hydrogen bonds to form C2(1)(4) chains; each cation is linked by C-H···O hydrogen bonds to two different chains, so forming a sheet structure. There are no direction-specific intermolecular interactions in the structure of (II).
authors.affiliation: Chemical Sciences, Vittal Mallya Scientific Research Foundation (VMSRF), 94/3 and 94/5, 23rd Cross, 29th Main, BTM 2nd Stage, Bangalore 560 076, India.
authors.forename: Shivanna
authors.initials: S
authors.lastname: Shivaprakash
authors.affiliation: Chemical Sciences, Vittal Mallya Scientific Research Foundation (VMSRF), 94/3 and 94/5, 23rd Cross, 29th Main, BTM 2nd Stage, Bangalore 560 076, India.
authors.forename: G Chandrasekara
authors.initials: GC
authors.lastname: Reddy
authors.affiliation: Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA.
authors.forename: Jerry P
authors.initials: JP
authors.lastname: Jasinski
authors.affiliation: Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Millikan
authors.affiliation: Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA.
authors.forename: Courtney E
authors.initials: CE
authors.lastname: Duff
authors.affiliation: School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland.
authors.forename: Christopher
authors.initials: C
authors.lastname: Glidewell
mesh_terms: D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry*; D013267:Stilbenes / Q000737:chemistry*; D014320:Triphenylmethyl Compounds / Q000737:chemistry*
chemical_list: C000602493:2,2',4,4',5,5'-hexamethoxystilbene; D009943:Organophosphorus Compounds; D013267:Stilbenes; D014320:Triphenylmethyl Compounds; C000602492:triphenyl(2,4,5-trimethoxybenzyl)phosphonium chloride
keywords: Wittig reaction; crystal structure; hydrogen bonding; phosphonium salt; polyalkoxy-substituted stilbenes; steric congestion