The Reduction of α-X-Acetophenones (X = PhO, Br, Cl) in Hydrogen-Donating Solvents at Elevated Temperatures

Dorrestijn, Edwin; Hemmink, Sven; Hulstman, Guido; Monnier, Laurent; Scheppingen, Wibo B. van

doi:10.1002/(sici)1099-0690(199905)1999:5<1267::aid-ejoc1267>3.0.co;2-x

Cited by 3 publications

(1 citation statement)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The structure of lignin is a complicated network of aromatic ethers connected by several types of linkages in which arylglycerol β-aryl ether or β-O-4 linkages predominate, Scheme . A fundamental understanding of the decomposition pathways of lignin model compounds is important in quantifying the thermal reaction pathways of lignin-like structures under hydropyrolysis conditions, understanding the fate of lignin in the geosphere, and understanding the practical consequences of lignin reactivity, such as mechanisms of paper yellowing 1 …”

Section: Introductionmentioning

confidence: 99%

Model Compound Studies of the β-O-4 Linkage in Lignin: Absolute Rate Expressions for β-Scission of Phenoxyl Radical from 1-Phenyl-2-phenoxyethanol-1-yl Radical

2002

View full text Add to dashboard Cite

Arrhenius rate expressions were determined for beta-scission of phenoxyl radical from 1-phenyl-2-phenoxyethanol-1-yl, PhC*(OH)CH2OPh (V). Ketyl radical V was competitively trapped by thiophenol to yield PhCH(OH)CH2OPh in competition with beta-scission to yield phenoxyl radical and acetophenone. A basis rate expression for hydrogen atom abstraction by sec-phenethyl alcohol, PhC*(OH)CH3, from thiophenol, log(k(abs)/M(-1) s(-1)) = (8.88 +/- 0.24) - (6.07 +/- 0.34)/theta, theta = 2.303RT, was determined by competing hydrogen atom abstraction with radical self-termination. Self-termination rates for PhC*(OH)CH3 were calculated using the Smoluchowski equation employing experimental diffusion coefficients of the parent alcohol, PhCH(OH)CH3, as a model for the radical. The hydrogen abstraction basis reaction was employed to determine the activation barrier for the beta-scission of phenoxyl from 1-phenyl-2-phenoxyethanol-1-yl (V): log(k beta)/s(-1)) = (12.85 +/- 0.22) - (15.06 +/- 0.38)/theta, k beta (298 K) ca. (64.0 s(-1) in benzene), and log(k beta /s(-1)) = (12.50 +/- 0.18) - (14.46 +/- 0.30)/theta, k beta (298 K) = 78.7 s(-1) in benzene containing 0.8 M 2-propanol. B3LYP/cc-PVTZ electronic structure calculations predict that intramolecular hydrogen bonding between the alpha-OH and the -OPh leaving group of ketyl radical (V) stabilizes both ground- and transition-state structures. The computed activation barrier, 14.9 kcal/mol, is in good agreement with the experimental activation barrier.

show abstract

Section: Introductionmentioning

confidence: 99%

Model Compound Studies of the β-O-4 Linkage in Lignin: Absolute Rate Expressions for β-Scission of Phenoxyl Radical from 1-Phenyl-2-phenoxyethanol-1-yl Radical

2002

View full text Add to dashboard Cite

show abstract

Thermal Stability of 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) and Related N-Alkoxyamines

et al. 1999

Self Cite

View full text Add to dashboard Cite

The carbon-oxygen bond dissociation enthalpies, BDE(C-O), in several N-alkoxyamine derivatives based on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) have been determined in the liquid phase by photoacoustic calorimetry. The BDE(C-O) and the BDE(C-H) in the corresponding hydrocarbons follow a linear correlation: BDE(C-O) ) 1.04BDE(C-H) -62.1 kcal mol -1 . When an electronegative element adjacent to the C-O bond is present, as in tetrahydrofuryl, a substantial deviation from the correlation is noticed. Due to the anomeric interaction the (THF) N-alkoxyamine is stabilized by an additional 14 kcal mol -1 . The Arrhenius expression for the homolytic decomposition of methyl-TEMPO in the gas phase obeys k/s -1 ) 10 15.3 exp(-45.3/RT) to yield a BDE(C-O) of 47 ( 1 kcal mol -1 at 298 K. Furthermore, a high reactivity of TEMPO toward hydrogen donors, 1,4-cyclohexadiene or 9,10-dihydroanthracene, has been observed. Above 380 K, TEMPO is converted into the hydroxyamine 2,2,6,6-tetramethyl-1-piperidinol (TEMPOH) and the amine 2,2,6,6tetramethylpiperidine (TEMPH). An acid-catalyzed mechanism for TEMPO deoxygenation is proposed.

show abstract

The International legal framework for countering International crimes in Afghanistan

Bazov¹

2021

Legal Ukraine

View full text Add to dashboard Cite

The article examines the international legal framework for combating international crimes in Afghanistan. The issues of the jurisdiction of the International Criminal Court in relation to the prosecution and prosecution of persons who have committed or ordered to commit war crimes, crimes against humanity and terrorist acts in a given country are analyzed. Attention is drawn to the organizational problems in the activities of the International Criminal Court in connection with the application of sanctions against judges and the prosecutor of this court. The situation with the perpetration of mass international crimes in Afghanistan and the need to bring to justice the perpetrators who killed or injured thousands of civilians in Afghanistan cannot but be alarmed by the international community, which sees the events in Afghanistan as a threat to peace and international security. As there is no effective domestic justice system for prosecuting international crimes in Afghanistan, the International Criminal Court is the most effective legal mechanism for prosecuting international criminals for committing war and other international crimes in Afghanistan. There are all the necessary preconditions for this – both the fact that the International Criminal Court, taking into account the principle of complementarity, has the necessary jurisdiction to investigate and prosecute individuals for committing international crimes, which were probably committed in Afghanistan, and that Afghanistan is a State party to the Rome Statute of the International Criminal Court and, accordingly, recognizes the jurisdiction of that court. At the same time, Afghanistan’s legal relations with the International Criminal Court in the field of combating international crimes must be carried out in accordance with international law, taking into account the principle of complementarity. Key words: international court, international crimes, jurisdiction, sanctions, responsibility.

show abstract

The Reduction of α-X-Acetophenones (X = PhO, Br, Cl) in Hydrogen-Donating Solvents at Elevated Temperatures

Cited by 3 publications

References 38 publications

Model Compound Studies of the β-O-4 Linkage in Lignin: Absolute Rate Expressions for β-Scission of Phenoxyl Radical from 1-Phenyl-2-phenoxyethanol-1-yl Radical

Model Compound Studies of the β-O-4 Linkage in Lignin: Absolute Rate Expressions for β-Scission of Phenoxyl Radical from 1-Phenyl-2-phenoxyethanol-1-yl Radical

Thermal Stability of 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) and Related N-Alkoxyamines

The International legal framework for countering International crimes in Afghanistan

Contact Info

Product

Resources

About