Nucleophilic Attack on(π-Allyl)palladium Complexes: Direction of the Attack to the Central or Terminal Carbon Atom by Ligand Control

1995 ◽  
Vol 34 (22) ◽  
pp. 2551-2553 ◽  
Author(s):  
Ana M. Castaño ◽  
Attila Aranyos ◽  
Kálmán J. Szabó ◽  
Jan-E. Bäckvall
Keyword(s):  
Carbon Atom ◽  
Palladium Complexes ◽  
Nucleophilic Attack ◽  
Terminal Carbon Atom

scholarly journals Understanding the reaction mechanism of the regioselective piperidinolysis of aryl 1-(2,4-dinitronaphthyl) ethers in DMSO: Kinetic and DFT studies

2021 ◽  
Vol 46 ◽  
pp. 146867832110274
Author(s):  
Yasmen M Moghazy ◽  
Nagwa MM Hamada ◽  
Magda F Fathalla ◽  
Yasser R Elmarassi ◽  
Ezzat A Hamed ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Density Functional ◽  
Function Analysis ◽  
Density Functional Theory Method ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Nucleophilic Attack ◽  
Common Mechanism ◽  
Slow Step ◽  
Rate Determining Step

Reactions of aryl 1-(2,4-dinitronaphthyl) ethers with piperidine in dimethyl sulfoxide at 25oC resulted in substitution of the aryloxy group at the ipso carbon atom. The reaction was measured spectrophotochemically and the kinetic studies suggested that the titled reaction is accurately third order. The mechanism is began by fast nucleophilic attack of piperidine on C1 to form zwitterion intermediate (I) followed by deprotonation of zwitterion intermediate (I) to the Meisenheimer ion (II) in a slow step, that is, SB catalysis. The regular variation of activation parameters suggested that the reaction proceeded through a common mechanism. The Hammett equation using reaction constant σo values and Brønsted coefficient value showed that the reaction is poorly dependent on aryloxy substituent and the reaction was significantly associative and Meisenheimer intermediate-like. The mechanism of piperidinolysis has been theoretically investigated using density functional theory method using B3LYP/6-311G(d,p) computational level. The combination between experimental and computational studies predicts what mechanism is followed either through uncatalyzed or catalyzed reaction pathways, that is, SB and SB-GA. The global parameters of the reactants, the proposed activated complexes, and the local Fukui function analysis explained that C1 carbon atom is the most electrophilic center of ether. Also, kinetics and theoretical calculation of activation energies indicated that the mechanism of the piperidinolysis passed through a two-step mechanism and the proton transfer process was the rate determining step.

Hydroboration of acyclic allenes with disiamylborane

1969 ◽  
Vol 47 (6) ◽  
pp. 1083-1086 ◽  
Author(s):  
D. S. Sethi ◽  
G. C. Joshi ◽  
D. Devaprabhakara
Keyword(s):  
Carbon Atom ◽  
Transition State ◽  
Steric Effects ◽  
Electrophilic Attack ◽  
Terminal Carbon Atom ◽  
Central Carbon Atom ◽  
Central Carbon

The present investigation demonstrates the hydroboration of 1,2-nonadiene, phenylpropadiene, 3-phenyl-1,2-butadiene, 4,5-nonadiene, and tetramethylallene with disiamylborane. All the allenes except tetramethylallene underwent 100% conversion. Examination of the products indicated preferential electrophilic attack of boron on the least substituted terminal carbon atom in the case of 1,2-nonadiene, phenylpropadiene, 3-phenyl-1,2-butadiene, and on the central carbon atom in 4,5-nonadiene. In tetramethylallene boron, attack was exclusively on the central carbon atom. These results have been explained in terms of steric effects on a four-centered transition state.

scholarly journals QUANTUM-CHEMICAL STUDY OF THE REACTION MECHANISM 1,2-ETHANEDIIOL WITH 1,3-DICHLOROPROPENE

2020 ◽  
Vol 2018 (1) ◽  
pp. 56-57
Author(s):  
Elena Chirkina ◽  
Leonid Krivdin ◽  
Nikolay Korchevin
Keyword(s):  
Carbon Atom ◽  
Sulfur Atom ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Thiol Group ◽  
Chemical Study ◽  
Nucleophilic Attack ◽  
Substitution Product ◽  
Reaction Proceeds ◽  
Theoretical Mechanism

The theoretical mechanism of the interaction of 1,3-dichloropropene with 1,2- ethanedithiol in the system "hydrazine hydrate-KOH" has been proposed by the method of B3LYP / 6- 311 ++ G (d, p) in the framework of the theory of the electron-density functional according to which the reaction proceeds successively in several stages, including the nucleophilic substitution of the chlorine atom present in the sp3-hybridized carbon atom with a sulfur atom to form a mono-substitution product that undergoes a prototropic allylic rearrangement that migrates the double bond to the sulfur atom, followed by closure in the dithiolane cycle due to the nucleophilic attack of the sulfide anion of the second thiol group of the reagent per carbon atom located in the γ-position with respect to the second chlorine atom.

scholarly journals THEORETICAL STUDY OF THE REACTION MECHANISM 1,2-ETHANEDIIOL WITH 1,3-DICHLOROPROPENE

2020 ◽  
Vol 2018 (1) ◽  
pp. 68-77
Author(s):  
Elena Chirkina ◽  
Leonid Krivdin ◽  
Nikolay Korchevin
Keyword(s):  
Carbon Atom ◽  
Chlorine Atom ◽  
Sulfur Atom ◽  
Density Functional ◽  
Theoretical Study ◽  
Thiol Group ◽  
Nucleophilic Attack ◽  
Substitution Product ◽  
Reaction Proceeds ◽  
Theoretical Mechanism

The theoretical mechanism of the interaction of 1,3-dichloropropene with 1,2-ethanedithiol in the system "hydrazine hydrate-KOH" has been proposed by the method of B3LYP / 6-311 ++ G (d, p) in the framework of the theory of the electron-density functional according to which the reaction proceeds successively in several stages, including the nucleophilic substitution of the chlorine atom present in the sp3-hybridized carbon atom with a sulfur atom to form a mono-substitution product that undergoes a prototropic allylic rearrangement that migrates the double bond to the sulfur atom, followed by closure in the dithiolane cycle due to the nucleophilic attack of the sulfide anion of the second thiol group of the reagent per carbon atom located in the γ-position with respect to the second chlorine atom.

scholarly journals Synthesis and crystal structures of two purpurin derivatives: 1,4-dihydroxy-2-propoxyanthraquinone and 2-butoxy-1,4-dihydroxyanthraquinone

2017 ◽  
Vol 73 (11) ◽  
pp. 1687-1691 ◽  
Author(s):  
Eric Bosch ◽  
Emily N. McClain
Keyword(s):  
Carbon Atom ◽  
Hydrogen Bonds ◽  
Sodium Hydride ◽  
Maximum Deviation ◽  
Independent Molecule ◽  
Asymmetric Unit ◽  
Terminal Carbon Atom ◽  
Butyl Group ◽  
Independent Molecules ◽  
Hydroxy Groups

The title compounds were obtained by deprotonation of 1,2,4-trihydroxyanthraquinone (purpurin) using sodium hydride followed by reaction with either 1-bromopropane or 1-bromobutane. 1,4-Dihydroxy-2-propoxyanthraquinone crystallizes as a 1:1 solvate from acetonitrile, C17H14O5·CH3CN. The anthraquinone core of the molecule is essentially planar and both hydroxy groups participate in intramolecular O—H...O (carbonyl) hydrogen bonds. The propyl chain is angled slightly above the plane of the anthraquinone moiety with a maximum deviation of 0.247 (2) Å above the plane for the terminal carbon atom. In contrast, 2-butoxy-1,4-dihydroxyanthraquinone, C18H16O5, crystallizes from nitromethane with two independent molecules in the asymmetric unit. The anthraquinone core of each independent molecule is essentially planar and both hydroxy groups on both molecules participate in intramolecular O—H...O(carbonyl) hydrogen bonds. The butyl chain in one molecule is also angled slightly above the plane of the anthraquinone moiety, with a maximum deviation of 0.833 (5) Å above the plane for the terminal carbon atom. In contrast, the butyl group on the second molecule is twisted out of the plane of the anthraquinone core with a torsion angle of 65.1 (3)°, resulting in a maximum deviation of 1.631 (5) Å above the plane for the terminal carbon atom.

The consequences of steric effects in the cleavage step of the sulfohaloform reaction

1979 ◽  
Vol 57 (16) ◽  
pp. 2185-2190 ◽  
Author(s):  
Denis George Kay ◽  
Richard Francis Langler ◽  
June Ellen Trenholm
Keyword(s):  
Carbon Atom ◽  
Chloride Ions ◽  
Nucleophilic Attack ◽  
Steric Effects ◽  
Water Molecules ◽  
Sulfonyl Group ◽  
Cleavage Step

The pathway for the aqueous chlorinolysis of a series of β-sulfonyl-sulfides is elucidated and the SN2 cleavage step examined. Steric effects in the cleavage of the α-polychloro-oxochloro-sulfonium chloride intermediates are held to be responsible for the suppression of the established nucleophilic competition between water molecules and chloride ions with the result that all cleavage products arise from nucleophilic attack by chloride ions. This report details the second known example of successful SN2 displacement on a carbon atom α to a sulfonyl group.

Intramolecular Diels-Alder Additions of Benzynes to Furans. Exploratory Studies

1986 ◽  
Vol 39 (4) ◽  
pp. 635 ◽  
Author(s):  
WM Best ◽  
D Wege
Keyword(s):  
Carboxylic Acid ◽  
Carbon Atom ◽  
Anthranilic Acid ◽  
Furan Ring ◽  
Alkoxy Group ◽  
Diels Alder ◽  
Ring Systems ◽  
Terminal Carbon Atom ◽  
Furan Moiety

A series of 3-alkoxyanthranilic acids, in which a furan ring is attached to the terminal carbon atom of the alkoxy group, has been prepared. When the chain linking the anthranilic acid and furan ring systems is three or four atoms long, decomposition of the derived diazonium chlorides generates the corresponding benzynes , which are efficiently trapped intramolecularly by the furan moiety. Diazotization of 2-amino-3-furfuryloxybenzoic acid, where the linking chain is two atoms long, results in fragmentation with the formation of 6-diazo-5- oxocyclohexa-1,3-diene-1-carboxylic acid.

MINDO-Forces Study of Phenyl and Cyclopropyl Substituted Allyl Cations and Anions

1987 ◽  
Vol 42 (3) ◽  
pp. 297-304
Author(s):  
Hayfa M. Jarjis ◽  
Salim M. Khalil
Keyword(s):  
Carbon Atom ◽  
Energy Minimization ◽  
Phenyl Ring ◽  
Terminal Carbon Atom ◽  
Allyl Cation ◽  
Allyl Anions

MINDO-force calculations have been performed on phenyl and cyclopropyl substituted allyl cations and anions with complete energy minimization. It is found that the phenyl ring destabilizes the allyl cations when substituted at the terminal and at the center carbon atom of the cation, while the cyclopropyl ring stabilizes the allyl cation when substituted at the terminal carbon atoms, but destabilizes the cation when substituted at the center carbon atom of the cation. These results agree with the experimental ones. In the case of the allyl anions, it is found that the phenyl ring destabilizes the allyl anions when substituted on the terminal and on the center carbon atoms of the allyl anions, while the cyclopropyl ring stabilizes the allyl anion when substituted on the terminal carbon atom but destabilizes the anion when substituted on the center carbon atom. Also, it is found that both the phenyl and cyclopropyl rings are electron withdrawing when substituted on the allyl anions, while they are electron donating when substituted on the allyl cations.

The hydration of mesitylketene in aqueous solution: detection of acid catalysis for an aromatic ketene

1995 ◽  
Vol 73 (4) ◽  
pp. 539-543 ◽  
Author(s):  
J. Andraos ◽  
A.J. Kresge ◽  
N.P. Schepp
Keyword(s):  
Aqueous Solution ◽  
Carbon Atom ◽  
Perchloric Acid ◽  
Reaction Rate ◽  
Acid Catalysis ◽  
Sodium Perchlorate ◽  
Nucleophilic Attack ◽  
Acid Solutions ◽  
Uncatalyzed Reaction ◽  
Acid Catalyzed

Mesitylketene was generated flash photolytically in aqueous solution by the photo-Wolff reaction of 2,4,6-trimethyldiazoacetophenone and also by rearrangement of mesitylynol obtained through photodecarbonylation of mesitylhydroxycyclopropenone, and rates of hydration of this ketene were measured in dilute perchloric acid, sodium perchlorate, and sodium hydroxide solutions as well as in concentrated sodium perchlorate and perchloric acid solutions. In dilute solution only an uncatalyzed reaction and a sodium-hydroxide-catalyzed process were observed, both of which could be attributed to nucleophilic attack, by water and by hydroxide ion, respectively, at the ketene carbonyl carbon atom. In concentrated sodium perchlorate solutions, a mild decrease in reaction rate with increasing salt concentration was observed, as expected on the basis of decreasing water activity and a consequent slowing of the uncatalyzed reaction. A similar mild decrease was found in perchloric acid solutions up to [Formula: see text] but this then gave way to a rate increase that became dominant above [Formula: see text] This appearance of acid catalysis indicates a change in reaction mechanism from nucleophilic attack of water to an electrophilic process involving rate-determining protonation on the β-carbon atom of the ketene group. Analysis of the acid-catalyzed reaction rate by the Cox–Yates method gives the catalytic coefficient [Formula: see text] This, when compared with [Formula: see text] for ketene itself, shows that the mesityl group retards acid-catalyzed hydration by a factor of 2200, and consequently the acid-catalyzed reaction of this, and other aromatic ketenes as well, becomes apparent only under strongly acidic conditions. Keywords: mesitylketene, ketene hydration, acid catalysis, Cox–Yates excess acidity correlation.

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