1556-08-7Relevant articles and documents
Spectroscopic Analyses on Reaction Intermediates Formed during Chlorination of Alkanes with NaOCl Catalyzed by a Nickel Complex
Draksharapu, Apparao,Codolà, Zoel,Gómez, Laura,Lloret-Fillol, Julio,Browne, Wesley R.,Costas, Miquel
, p. 10656 - 10666 (2015)
The spectroscopic, electrochemical, and crystallographic characterization of [(Me,HPyTACN)NiII(CH3CN)2](OTf)2 (1) (Me,HPyTACN = 1-(2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane, OTf = CF3SO3) is described together with its reactivity with NaOCl. 1 catalyzes the chlorination of alkanes with NaOCl, producing only a trace amount of oxygenated byproducts. The reaction was monitored spectroscopically and by high resolution electrospray-mass spectrometry (ESI-MS) with the aim to elucidate mechanistic aspects. NaOCl reacts with 1 in acetonitrile to form the transient species [(L)NiII-OCl(S)]+ (A) (L = Me,HPyTACN, S = solvent), which was identified by ESI-MS. UV/vis absorption, electron paramagnetic resonance, and resonance Raman spectroscopy indicate that intermediate A decays to the complex [(L)NiIII-OH(S)]2+ (B) presumably through homolytic cleavage of the O-Cl bond, which liberates a Cl? atom. Hydrolysis of acetonitrile to acetic acid under the applied conditions results in the formation of [(L)NiIII-OOCCH3(S)]2+ (C), which undergoes subsequent reduction to [(L)NiII-OOCCH3(S)]2+ (D), presumably via reaction with OCl- or ClO2-. Subsequent addition of NaOCl to [(L)NiII-OOCCH3(S)]+ (D) regenerates [(L)NiIII-OH(S)]2+ (B) to a much greater extent and at a faster rate. Addition of acids such as acetic and triflic acid enhances the rate and extent of formation of [(L)NiIII-OH(S)]2+ (B) from 1, suggesting that O-Cl homolytic cleavage is accelerated by protonation. Overall, these reactions generate Cl? atoms and ClO2 in a catalytic cycle where the nickel center alternates between Ni(II) and Ni(III). Chlorine atoms in turn react with the C-H bonds of alkanes, forming alkyl radicals that are trapped by Cl? to form alkyl chlorides.
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Traynham,J.G.,Couvillon,T.M.
, p. 3205 - 3211 (1967)
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Allinger,N.L.,Tushaus,L.A.
, p. 2051 - 2059 (1967)
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Silica gel-mediated hydrohalogenation of unactivated alkenes using hydrohalogenic acids under organic solvent-free conditions
Tanemura, Kiyoshi
supporting information, p. 4293 - 4298 (2018/11/10)
Silica gel-mediated hydrochlorination of unactivated alkenes using 35% hydrochloric acid under organic solvent-free conditions proceeded to give the corresponding chlorides in good yields. Hydrobromination or hydriodination using 47% hydrobromic acid or 55% hydriodic acid afforded the corresponding halides, respectively. Silica gel could be recycled five times without any significant loss of activities.
Highly selective halogenation of unactivated C(sp3)-H with NaX under co-catalysis of visible light and Ag@AgX
Liu, Shouxin,Zhang, Qi,Tian, Xia,Fan, Shiming,Huang, Jing,Whiting, Andrew
, p. 4729 - 4737 (2018/10/23)
The direct selective halogenation of unactivated C(sp3)-H bonds into C-halogen bonds was achieved using a nano Ag/AgCl catalyst at RT under visible light or LED irradiation in the presence of an aqueous solution of NaX/HX as a halide source, in air. The halogenation of hydrocarbons provided mono-halide substituted products with 95% selectivity and yields higher than 90%, with the chlorination of toluene being 81%, far higher than the 40% conversion using dichlorine. Mechanistic studies demonstrated that the reaction is a free radical process using blue light (450-500 nm), with visible light being the most effective light source. Irradiation is proposed to cause AgCl bonding electrons to become excited and electron transfer from chloride ions induces chlorine radical formation which drives the substitution reaction. The reaction provides a potentially valuable method for the direct chlorination of saturated hydrocarbons.
