Reactivity of C-H bonds in cyclohexanone and 1-tert-butylperoxycyclohexanol toward the tert-butylperoxyl radical

The kinetics of oxygen uptake and the composition of the cyclohexanone oxidation products in the azobisisobutyronitrile-initiated oxidation of cyclohexanone in the presence of tert-butyl hydroperoxide have been investigated by the Howard-Ingold method. The partial rate constants of the reaction of the tert-butylperoxyl radical with the C-H bonds of cyclohexanol and 1-tert-butylperoxycyclohexanole at 333 K have been determined. The carbonyl group of cyclohexanone activates the C-H bonds in the 2- and 6-positions (α) and deactivates the C-H bonds in the 3- and 5-positions (β) compared to the C-H bonds in the 4-position (γ), whose reactivity is similar to that of the methylenic C-H bonds in cyclohexane. Evaluation of the joint effect of the hydroxyl and tert-butylperoxyl groups in 1-tert-butylperoxycyclohexanol suggests a considerable deactivation of the C-H bonds in the 2- and 6-positions (β) and, to a lesser extent, in the 3- and 5-positions (γ).     

Reactivity of the 5-hexenyl radical toward the anion of 2-nitropropane and borohydride anion

The 5-hexenyl radical adds to the anion of 2-nitropropane with a rate constant of ≈ × 10⁶ L/mol-s at 40°. Hydrogen atom abstraction from BH₄^? occurs more slowly than abstraction from CH₃O^? and with a rate constant less than 1 × 10⁴ L/mol-s at 30°. The reaction of Δ⁵- hexenylmercury chloride with sodium borohydride in MeOH/NaOH proceeds via hydrogen abstraction by the hexenyl radical from RHgH and not from NaBH₄.     

Reactivity of substituted charged phenyl radicals toward components of nucleic acids

Reactions of differently substituted phenyl radicals with components of nucleic acids have been investigated in the gas phase. A positively charged group located meta with respect to the radical site was employed to allow manipulation of the radicals in a Fourier-transform ion cyclotron resonance mass spectrometer. All of these electrophilic radicals react with sugars via exclusive hydrogen atom abstraction, with adenine and uracil almost exclusively via addition (likely at the C8 and C5 carbons, respectively), and with the nucleoside thymidine by hydrogen atom abstraction and addition at C5 in the base moiety (followed by elimination of (*)CH(3)). These findings parallel the reactivity of the phenyl radical with components of nucleic acids in solution, except that the selectivity for addition is different. Like HO(*), the electrophilic charged phenyl radicals appear to favor addition to the C5-end of the C5-C6 double bond of thymine and thymidine, whereas the phenyl radical preferentially adds to C6. The charged phenyl radicals do not predominantly add to thymine, as the neutral phenyl radical and HO(*), but mainly react by hydrogen atom abstraction from the methyl group (some addition to C5 in the base followed by loss of (*)CH(3) also occurs). Adenine appears to be the preferred target among the nucleobases, while uracil is the least favored. A systematic increase in the electrophilicity of the radicals by modification of the radicals' structures was found to facilitate all reactions, but the addition even more than hydrogen atom abstraction. Therefore, the least reactive radicals are most selective toward hydrogen atom abstraction, while the most reactive radicals also efficiently add to the base. Traditional enthalpy arguments do not rationalize the rate variations. Instead, the rates reflect the radicals' electron affinities used as a measure for their ability to polarize the transition state of each reaction.     

Friedel-Crafts alkylation of benzene by normal ω-chloroalkanoic acids and their methyl esters and nitriles

Conclusions In the alkylation of benzene by -chloroalkanoic acids Cl(CH₂)_nCOOH (where n=3–6) and their methyl esters and nitriles, in the presence of A1C1₃, the degree of isomerization of the alkyl chain is less than with the corresponding 1-chloroalkanes, depending on the increase in electron acceptor activity in the sequence HOOC-> CH₃OCO-> CN-.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 367–371, February, 1987.     

Reactivity of the C-H bonds of methyl hexanoate toward the <Emphasis Type="Italic">tert</Emphasis>-butylperoxy radical

The kinetics of oxygen uptake and the kinetics of accumulation of methyl hexanoate oxidation products in the presence of tert-butyl hydroperoxide have been investigated to determine the partial rate constants for the interaction of the tert-butylperoxy radical with C-H bonds of the ester at 373 K. The ester group deactivates the C-H bonds in the 2- and 3-positions and does not deactivate the same bonds in the 5-position, which are similar in reactivity to the methylenic C-H bonds of hydrocarbons. The C-H bonds of the methoxyl group of methyl hexanoate are substantially more reactive than the C-H bonds of the methyl group.     

Reactivity of substituted benzoic acids and their complexes with 2,4,6-trinitrotoluene toward diphenyldiazomethane

The reactions of 2,4-dihydroxybenzoic and 4-aminobenzoic acids with diphenyldiazomethane are accelerated in the presence of 2,4,6-trinitrotoluene as π-acceptor. The catalytic effect of the latter is determined by the formation of charge-transfer complexes with the acids, which facilitates proton abstraction and stabilizes the corresponding anions.     

Reactivity of a trivalent phosphorus radical cation as an electrophile toward pyridine derivatives

The reaction of methylviologen (MV²⁺) with tributylphosphine ( 1p ) and diethylphenylphosphine ( 1q ) in the presence of an alkyl-substituted pyridine ( 2 ) was found to take place through a single-electron transfer (SET) from 1 to MV²⁺ followed by nucleophilic attack by 2 on the resulting phosphine radical cation 1 ^•+. Kinetic examination showed that, in the transition state for the reaction of 1 ^•+ with 2 , an unpaired electron is largely delocalized to the pyridine moiety. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:152–157, 2000     

Reactivity ratios in conventional and nickel-mediated radical copolymerization of methyl methacrylate and functionalized methacrylate monomers

Copolymerization of an excess of methyl methacrylate (MMA) relative to 2-hydroxyethyl methacrylate (HEMA) was carried out in toluene at 80 °C according to both conventional and controlled Ni-mediated radical polymerizations. Reactivity ratios were derived from the copolymerization kinetics using the Jaacks method for MMA and integrated conversion equation for HEMA (r_MMA = 0.62 ± 0.04; r_HEMA = 2.03 ± 0.74). Poly(ethylene glycol) α-methyl ether, ω-methacrylate (PEGMA, M_n = 475 g mol⁻¹) was substituted for HEMA in the copolymerization experiments and reactivity ratios were also determined (r_MMA = 0.75 ± 0.07; r_PEGMA ∼ 1.33). Both the functionalized comonomers were consumed more rapidly than MMA indicating the preferred formation of heterogeneous bottle-brush copolymer structures with bristles constituted by the hydrophilic (macro)monomers. Reactivity ratios for nickel-mediated living radical polymerization were comparable with those obtained by conventional free radical copolymerization. Interactions between functional monomers and the catalyst (NiBr₂(PPh₃)₂) were observed by ¹H NMR spectroscopy.     

Synthesis of nitriles of phenylferrocene-carboxylic acids

Conclusions The nitriles of 1-phenylferrocene-2-, -3-, and -1'-carboxylic and p-ferrocenylbenzoic acids have been obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1467–1469, August, 1966.     

Reactivity of Benzamide toward Sulfonylation

Russian Journal of Organic Chemistry - The ranges of variation of the rate constant (0.031– 0.153 L·mol–1·s–1), energy of activation (21– 55 kJ/mol), and entropy...     

Reactivity of phthalimide N-oxyl radical (PINO) toward the phenolic O-H bond. A kinetic study

The reactivity of the phthalimide N-oxyl radical (PINO) toward the OH bond of a series of substituted phenols was kinetically investigated in CH(3)CN. The reaction selectivity and the deuterium kinetic isotope effect were determined. Information on the kinetic solvent effect was also obtained with phenol as the substrate.     

Reactivity of trimethylcyanosilane toward the surface of silica

The reaction of the surface of silica with (CH₃)₃SiCN vapor was studied by IR spectroscopy. It was established that the chemisorption of trimethylcyanosilane belongs to the processes of electrophilic substitution of a proton in free silanol groups. The activation energy, calculated from the kinetic curves, amounts to 22±1 kJ/mole of grafted trimethylsilyl groups.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 117–120, January–February, 1987.     

Reactivity of Polysaccharide Aldehydes toward N-Nucleophiles

The conversion of aldehyde groups in polysaccharide aldehydes to azomethine groups in reactions with amines and hydrazine derivatives was studied in relation to the structure of polysaccharide aldehyde and reaction conditions.     

Reactivity of Phosphaalkenes toward Carbene Complexes

Reaction of phosphaalkenes RP=C(NMe 2 ) 2 (R = t -Bu, Me 3 Si), featuring an inverse distribution of electron density about the P--C double bond, with Fischer carbene complexes [(CO) 5 M=C(OEt)Ar] (Ar=Ph, 2-MeC 6 H 4 , 2-MeOC 6 H 4 , M = Cr, W) afforded a mixture of complexes [(CO) 5 M{P(R)=C(NMe 2 ) 2 }] and [(CO) 5 M{P(R)=C(OEt)Ar}]. The treatment of phosphaalkene HP=C(NMe 2 ) 2 with compound [(CO) 5 W=C(OEt)(2-MeOC 6 H 4 )] gives rise to the formation of an ( E / Z )-mixture of [(CO) 5 W{P(CH(NMe 2 ) 2 )=C(OEt)(2-MeOC 6 H 4 )}].     

Reactivity of Arylhydrazones toward Molecular Oxygen

The kinetics and mechanism of reaction of arylhydrazones with molecular oxygen were studied by gas volumetry. The reaction rate was studied in relation to the structure of arylhydrazone and kind of the solvent. The inhibiting power of the compounds toward initiated oxidation of ethylbenzene was evaluated, and the most effective compounds were found, judging from the ratio of the rate constants of the reactions with molecular oxygen and with peroxy radicals arising in the course of ethylbenzene oxidation.     

Reactivity of digallane toward nitrogen-containing compounds

The reactions of [LGa–GaL] (L = dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) with ammonia and pyrrolidine in toluene lead to the formation of adducts [L(NH₃)Ga–Ga(NH₃)L], [L(HNC₄H₈)Ga–GaL] and [L(HNC₄H₈)Ga–Ga(HNC₄H₈)L], respectively. In contrast, the reaction between crystalline digallane and an excess of pyrrolidine leads to the formation of compound [LGa(NC₄H₈)(HNC₄H₈)]. The complex [LGa(C₅H₅N)(μ-O)Ga(C₅H₅N)L] was obtain from reaction of digallane with N₂O in the presence of pyridine.     

Electron-transfer reaction of cinnamic acids and their methyl esters with the DPPH(*) radical in alcoholic solutions

The kinetic behavior of cinnamic acids, their methyl esters, and two catechols 1-10 (ArOH) in the reaction with DPPH(*) in methanol and ethanol is not compatible with a reaction mechanism that involves hydrogen atom abstraction from the hydroxyl group of 1-10 by DPPH(*). The rate of this reaction at 25 degrees C is, in fact, comparatively fast despite that the phenolic OH group of ArOH is hydrogen bonded to solvent molecules. The observed rate constants (k(1)) relative to DPPH(*) + ArOH are 3-5 times larger for the methyl esters than for the corresponding free acids and, for the latter, decrease as their concentration is increased according to the relation k(1) = B/[ArOH](0)(m), where k(1) is given in units of M(-1) s(-1), m is ca. 0.5, and B ranges from 0.02 (p-coumaric acid) to ca. 3.48 (caffeic acid) in methanol and from 0.04 (p-coumaric acid) to ca. 13 (sinapic acid) in ethanol. Apparently, the reaction mechanism of DPPH(*) + ArOH involves a fast electron-transfer process from the phenoxide anion of 1-10 to DPPH(*). Kinetic analysis of the reaction sequence for the free acids leads to an expression for the observed rate constant, k(1), proportional to [ArOH](0)(-1/2) in excellent agreement with the experimental behavior of these phenols. The experimental results are also interpreted in terms of the influence that adventitious acids or bases present in the solvent may have. These impurities dramatically influence the ionization equilibrium of phenols and cause a reduction or an enhancement, respectively, of the measured rate constants.     

Umpolung Reactivity of Aldehydes toward Carbon Dioxide

Carbon dioxide is an intrinsically stable molecule. Therefore, its activation requires extra energy input in the form of reactive reagents and/or activated catalysts and, often, harsh reaction conditions. Reported here is a direct carboxylation reaction of aromatic aldehydes with carbon dioxide to afford α‐keto acids as added‐value products. In situ generation of a reactive cyanohydrin was the key to the successful carboxylation reaction under operationally mild reaction conditions (25–40 °C, 1 atm CO₂). The resulting α‐keto acids served as a platform for α‐amino acid synthesis by reductive amination reactions, illustrating the chemical synthesis of essential bioactive molecules from carbon dioxide.