http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Hoque, Md. Ehtesham Ul,Dey, Nilay Kumar,Guha, Arun Kanti,Kim, Chan-Kyung,Lee, Bon-Su,Lee, Hai-Whang Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.10
The kinetics and mechanism of the nucleophilic substitution reactions of diphenyl phosphinic (1) and thiophosphinic (2) chlorides with substituted X-pyridines are investigated kinetically in acetonitrile at 35.0 and 55.0 oC, respectively. A concerted mechanism with backside nucleophilic attack is proposed for the pyridinolysis of 1, on the basis of the linear Bronsted plot with the βX value of 0.68. In the case of the pyridinolysis of 2, the Hammett and Bronsted plots are biphasic concave upwards with the break point at 3- phenyl pyridine. These results indicate a change in mechanism from a concerted SN2(P) process with direct backside nucleophilic attack for less basic nucleophiles (X = 3-CN-3-Ph) to a stepwise process with frontside attack for more basic nucleophiles (X = 4-MeO-3-Ph). Apparent secondary inverse kinetic isotope effects with deuterated pyridine (C5D5N), kH/kD < 1, are observed for the pyridinolysis of 1 and 2.
Kinetics and Mechanism of the Aminolysis of Diphenyl Phosphinic Chloride with Anilines
Md. Ehtesham Ul Hoque,Hai Whang Lee* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.6
The aminolyses of diphenyl phosphinic chloride (1) with substituted anilines in acetonitrile at 55.0 oC are investigated kinetically. Large Hammett r X (r nuc = 4.78) and Brnsted b X (b nuc = 1.69) values suggest extensive bond formation in the transition state. The primary normal kinetic isotope effects (kH/kD = 1.42-1.82) involving deuterated aniline (XC6H4ND2) nucleophiles indicate that hydrogen bonding results in partial deprotonation of the aniline nucleophile in the rate-limiting step. The faster rate of diphenyl phosphinic chloride (1) than diphenyl chlorophosphate (2) is rationalized by the large proportion of a frontside attack in the reaction of 1. These results are consistent with a concerted mechanism involving a partial frontside nucleophilic attack through a hydrogen-bonded, four-center type transition state.
Md. Ehtesham Ul Hoque,Nilay Kumar Dey,Arun Kanti Guha,김찬경,Bon-Su Lee*,Hai Whang Lee* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.10
The kinetics and mechanism of the nucleophilic substitution reactions of diphenyl phosphinic (1) and thiophosphinic (2) chlorides with substituted X-pyridines are investigated kinetically in acetonitrile at 35.0 and 55.0 oC, respectively. A concerted mechanism with backside nucleophilic attack is proposed for the pyridinolysis of 1, on the basis of the linear Brnsted plot with the bX value of 0.68. In the case of the pyridinolysis of 2, the Hammett and Brnsted plots are biphasic concave upwards with the break point at 3-phenyl pyridine. These results indicate a change in mechanism from a concerted SN2(P) process with direct backside nucleophilic attack for less basic nucleophiles (X = 3-CN-3-Ph) to a stepwise process with frontside attack for more basic nucleophiles (X = 4-MeO-3-Ph). Apparent secondary inverse kinetic isotope effects with deuterated pyridine (C5D5N), kH/kD < 1, are observed for the pyridinolysis of 1 and 2.
Kinetics and Mechanism of the Aminolysis of Diphenyl Phosphinic Chloride with Anilines
Ul Hoque, Md.Ehtesham,Lee, Hai-Whang Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.6
The aminolyses of diphenyl phosphinic chloride (1) with substituted anilines in acetonitrile at 55.0 oC are investigated kinetically. Large Hammett ρ X (ρnuc = ?4.78) and Bronsted β X (βnuc = 1.69) values suggest extensive bond formation in the transition state. The primary normal kinetic isotope effects (kH/kD = 1.42-1.82) involving deuterated aniline (XC6H4ND2) nucleophiles indicate that hydrogen bonding results in partial deprotonation of the aniline nucleophile in the rate-limiting step. The faster rate of diphenyl phosphinic chloride (1) than diphenyl chlorophosphate (2) is rationalized by the large proportion of a frontside attack in the reaction of 1. These results are consistent with a concerted mechanism involving a partial frontside nucleophilic attack through a hydrogen-bonded, four-center type transition state.
Ul Hoque, Md. Ehtesham,Guha, Arun Kanti,Kim, Chan Kyung,Lee, Bon-Su,Lee, Hai Whang Royal Society of Chemistry 2009 Organic & Biomolecular Chemistry Vol.7 No.14
<P>The nucleophilic substitution reactions of Y-<I>O</I>-aryl methyl phosphonochloridothioates with substituted anilines (XC<SUB>6</SUB>H<SUB>4</SUB>NH<SUB>2</SUB>) and deuterated anilines (XC<SUB>6</SUB>H<SUB>4</SUB>ND<SUB>2</SUB>) are investigated kinetically in acetonitrile at 55.0 °C. The Hammett and Brønsted plots for substituent (X) variations in the nucleophiles are biphasic concave downwards with a break region between X = H and 4-Cl. The deuterium kinetic isotope effects (DKIEs) are primary normal (<I>k</I><SUB>H</SUB>/<I>k</I><SUB>D</SUB> = 1.03–1.30) for stronger nucleophiles (X = 4-MeO, 4-Me and H), and <I>extremely large</I> secondary inverse (<I>k</I><SUB>H</SUB>/<I>k</I><SUB>D</SUB> = 0.367–0.567) for weaker nucleophiles (X = 4-Cl, 3-Cl and 3-NO<SUB>2</SUB>). The cross-interaction constants are negative (<I>ρ</I><SUB>XY(H)</SUB> = −0.95 and <I>ρ</I><SUB>XY(D)</SUB> = −1.11) for stronger nucleophiles, while positive (<I>ρ</I><SUB>XY(H)</SUB> = +0.77 and <I>ρ</I><SUB>XY(D)</SUB> = +0.21) for weaker nucleophiles. These kinetic results indicate that the mechanism changes from a concerted process involving frontside nucleophilic attack for stronger nucleophiles to a stepwise process with a rate-limiting leaving group expulsion from the intermediate involving backside attack for weaker nucleophiles. A hydrogen-bonded, four-center-type transition state (TS) is suggested for a frontside attack, while a trigonal bipyramidal pentacoordinate TS is suggested for a backside attack. The <I>unusually small</I> DKIEs, as small as or equal to 0.4, for weaker nucleophiles seem to be ascribed to severe steric congestion in the TS.</P> <P>Graphic Abstract</P><P>The title reactions, in MeCN at 55.0 °C, exhibit discrete non-linear free energy correlations. Deuterium kinetic isotope effects involving deuterated anilines (XC<SUB>6</SUB>H<SUB>4</SUB>ND<SUB>2</SUB>) are primary (<I>k</I><SUB>H</SUB>/<I>k</I><SUB>D</SUB> = 1.03–1.30) for stronger nucleophiles whereas they are extremely large secondary inverse (<I>k</I><SUB>H</SUB>/<I>k</I><SUB>D</SUB> = 0.367–0.567) for weaker nucleophiles. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b903148k'> </P>
Kinetics and Mechanism of the Anilinolysis of Diisopropyl Chlorophosphate in Acetonitrile
Md. Ehtesham Ul Hoque,이해황 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.9
The nucleophilic substitution reactions of diisopropyl chlorophosphate (3) with substituted anilines (XC_6H_4NH_2) and deuterated anilines (XC_6H_4NH_2) are investigated kinetically in acetonitrile at 55.0 oC. The anilinolysis rate of 3 is rather slow to be rationalized by the conventional stereoelectronic effects. The obtained deuterium kinetic isotope effects (DKIEs; kH/kD) are secondary inverse (kH/kD = 0.71-0.95) with maximum magnitude at X = H. A concerted mechanism involving predominant backside nucleophilic attack is proposed on the basis of the secondary inverse DKIEs.
Kinetics and Mechanism of the Anilinolysis of Diisopropyl Thiophosphinic Chloride in Acetonitrile
Md. Ehtesham Ul Hoque,이해황 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.11
The nucleophilic substitution reactions of diisopropyl thiophophinic chloride (3) with substituted anilines (XC_6H_4NH_2) and deuterated anilines (XC_6H_4ND_2) are investigated kinetically in acetonitrile at 65.0 ^oC. The anilinolysis rate of 3 is rather slow to be rationalized by the conventional stereoelectronic effects. The obtained deuterium kinetic isotope effects (DKIEs; kH/kD) are secondary inverse (kH/kD = 0.80-0.96). The anilinolyses of ten P=S systems in MeCN are reviewed on the basis of DKIEs and selectivity parameters to obtain systematic information on the DKIEs and mechanism for thiophosphoryl transfer reactions. The steric effects of the two ligands on reactivity, DKIEs, mechanism, and substituent effects of the nucleophile (X) on the DKIEs are discussed.