39787-30-9

Upstream product

• 24650-42-8 2,2-dimethoxy-2-phenylacetophenone 
• 67-56-1 methanol 
• 501-65-5 diphenyl acetylene 
• 30928-28-0 α,β-dimethoxystilbene 

Downstream Products

• 66822-20-6 α,α'-dimethoxybenzyl radical 

Relevant academic research and scientific papers

Photoionization of α-alkoxybenzyl radicals to yield α-alkoxybenzyl cations. Photochemistry of ω,ω-dimethoxy-ω-phenylacetophenone in polar solvents at high light intensities

On photolysis of the photopolymerization initiator PhC(O)C(OMe)2Ph in aqueous or alcoholic solution with 248 nm laser pulses or with 248 nm followed by 308 nm pulses (two-laser-two-colour technique), the short-lived species PhC.(OMe)2, PhC+(OMe)2 and e-solv were detected by their optical absorptions. The carbocation PhC+(OMe)2 and e-solv are the products of the monophotonic ionization of the radical PhC.(OMe)2 [φ(308 nm) = 0.2 in aqueous solution] generated from the parent, PhC(O)C(OMe)2Ph, by α-cleavage [φ(248 nm) ca. 0.5]. PhC+(OMe)2 reacts with water to produce the hemi-orthoester PhC(OMe)2OH and H+ which was identified by time-resolved conductance. PhC(OMe)2OH decomposes to yield PhC(O)OMe and MeOH (identified by GC). The α-alkoxybenzyl radicals PhCH.OR, produced by 248 nm photoinduced α-cleavage of the benzoin ethers PhC(O)CH(OR)Ph (R = Me, Et, Pri, But), also undergo ionization upon 248 or 308 nm photolysis. The rate constants for reaction of PhCH.OR with the oxidants Fe(CN)63-, Ir(Cl)62- and PhI2+ are on average 5.9 x 109, 4.2 x 109, 2.8 x 109 and 1.7 x 108 dm3 mol-1 s-1, respectively. From the facile photoionization of the α-alkoxybenzyl radicals it is concluded that this process may also take place under the typical high-intensity light conditions used in industrial photocuring, i.e. that the latter may involve cationic polymerization.

Geminal Substituent Effects. VIII. Enthalpies of Formation od Acetals

The standard enthalpies of combustion ΔHoc(1 or c) of the α-phenyl-substituted acetals (1) and diacetals (2) were measured calorimetrically.The enthalpies of vaporisation or sublimation ΔHvap or ΔHsub of 1-2 were obtained from the temperature function of the vapor pressure measured in a flow system, and the standard enthalpies of formation are obtained thereof: ΔH0f (l or c) and ΔHof (g) (in kJ mol-1 for 1a= -308.40+/-0.52(1), -248.94+/-0.88; 1b= -343.48+/-0.72(1), -288.5+/-1.5; 1c= -267.4+/-1.3(1), -205.3+/-1.3; 1d = -343.8+/-2.1 (c), -261.9+/-2.2; 1e = -397.02+/-0.86 ( c), -311.3+/-1.2; 1f = -414.52+/-0.80 (1), -350.68+/-0.86; 2a = -564.8+/-2.4 (c), -467.1+/-2.5; 2b = -547.6+/-1.6 (c), -414.9+/-2.7; 2c = -717.1+/-7.5 (c), -587.0+/-8.0.The results are combined into values of two strain free group increments CHPh> = -59.7 and CPh, C> = -71.3 kJ mol-1; and compared to the aliphatic series of acetals.

2,2-Dimethoxy-2-phenylacetophenone: Photochemistry and Free Radical Photofragmentation

Free radical reactions induced by photocleavage of the photocuring agent 2,2-dimethoxy-2-phenylacetophenone in oxygen-free solutions are investigated by product analysis, CIDNP, and by optical and ESR spectroscopy.It is shown that the photochemistry of the title compound is strong influenced by both thermal and photochemical fragmentations of the α,α-dimethoxybenzyl radical.A resulting light intensity dependence of product distributions and spectra has caused previous misinterpretations of reaction mechanisms, reaction kinetics, and spectral assignments.Detailed mechanisms, optical spectra, and kinetic data on self-terminations, thermal fragmentations, and additions to acrylonitrile of dimethoxybenzyl, benzoyl, and related radicals are reported.

Oxidation of Diphenylacetylene by I7+ and I5+ Compounds

The oxidation of diphenylacetylene with H5IO6 in acetic acid affords benzil.In methanol the principal products are the monoketal and the diketal of benzil, depending upon water content.Similar products are formed in methanol when I2O5 is the oxidizing agent.The latter and the alkyne in ethylene glycol afford benzil and the corresponding diketal.Both systems appear to require the presence of iodine for effective action.