Quantitative analysis and characterization of the products of the model reaction of n-butyllithium with excess 1,1-diphenylethylene: 1,1-Diphenylhexane and 1,1,3,3-tetraphenyloctane

Abstract

The model reaction of n-butyllithium with excess (11 M equivalents) 1,1-diphenylethylene (DPE) was reinvestigated using modern characterization techniques including SEC, one dimensional and two dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopy and electrospray ionization mass spectrometry (ESI MS). The products were the monoadduct, 1,1-diphenylhexane (nBuDPEH), and the diadduct, 1,1,3,3-tetraphenyloctane [nBu(DPE)2H], formed in 62 mol% and 38 mol% yields, respectively, as determined by SEC and 1H NMR spectroscopy. The 1H NMR spectrum of 1,1,3,3-tetraphenyloctane exhibited a terminal methine triplet resonance at δ 3.71 ppm that was uniquely coupled to the adjacent methylene doublet resonance at δ 3.09 ppm, located between the two carbons, each bonded to two phenyl groups [–C(C6H5)2-CH2-CH(C6H5)2. All of the characteristic 1H and 13C NMR resonances for both adducts were assigned using 2D NMR spectroscopic methods. The diadduct, nBu(DPE)2H, exhibited unique 13C NMR resonances at δ 50.79 ppm for the quaternary carbon resonance [CH2-C(C6H5)2−CH2], and at δ 43.74 ppm for the methylene group isolated between the two carbons, each bonded to two phenyl groups [–C(C6H5)2-CH2-CH(C6H5)2].