Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction, Part 13. The scope and limitations of the reaction with cyanide anion as the nucleophile

1997 ◽  
Vol 75 (8) ◽  
pp. 1055-1075 ◽  
Author(s):  
Donald R. Arnold ◽  
Kimberly A. McManus ◽  
Mary S.W. Chan
Keyword(s):  
Radical Cation ◽  
Oxidation Potential ◽  
Molecular Orbital Calculations ◽  
Aromatic Substitution ◽  
Radical Intermediate ◽  
Cyanide Anion ◽  
Alkyl Radicals ◽  
Alkyl Substitution ◽  
The Stability ◽  
High Level

The scope of the photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction has been extended to include cyanide anion as the nucleophile. Highest yields of adducts were obtained when the alkene or diene has an oxidation potential less than ca. 1.5 V (SCE). No adducts were obtained from 2-methylpropene (9), oxidation potential 2.6 V. Oxidation of cyanide anion, by the radical cation of the alkene or diene, can compete with the combination. With the alkenes, 2,3-dimethyl-2-butene (2) and 2-methyl-2-butene (10), both nitriles and isonitriles were obtained; isonitriles were not detected from the reactions involving the dienes, 2-methyl-1,3-butadiene (11), 2,3-dimethyl-1,3-butadiene (12), 4-methyl-1,3-pentadiene (13), 2,4-dimethyl-1,3-pentadiene (14), and 2,5-dimethyl-2,4-hexadiene (6). The specificity, nitrile versus isonitrile, is explained in terms of the Hard-Soft-Acid-Base (HSAB) principle. The photo-NOCAS reaction also occurs with the allene, 2,4-dimethyl-2,3-pentadiene (15), cyanide combining at the central carbon. Factors influencing the regiochemistry of the combination step, Markovnikov versus anti-Markovnikov, have been defined. Cyanide anion adds preferentially to the less alkyl-substituted, less sterically hindered, end of an unsymmetric alkene or conjugated diene radical cation, forming the more heavily alkyl-substituted radical intermediate. High-level abinitio molecular orbital calculations (MP2/6-31G*//HF/6-31G*) have been used to determine the effect of alkyl substitution on the stability of the intermediates, β-cyano and β-isocyano alkyl radicals, and products, alkyl cyanides and isocyanides. The more heavily alkyl-substituted radical is not necessarily the more stable. The product ratio (Markovnikov versus anti-Markovnikov) must be kinetically controlled. Keywords: photochemistry, radical ions, electron transfer, nitriles, isonitriles.

Photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction: methanol, beta-myrcene, and 1,4-dicyanobenzene. Intramolecular cyclization of an ene-diene radical cation

1998 ◽  
Vol 76 (9) ◽  
pp. 1238-1248 ◽  
Author(s):  
Donald R Arnold ◽  
Kimberly A McManus
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Radical Cations ◽  
Oxidation Potential ◽  
Molecular Orbital Calculations ◽  
Evidence Based ◽  
Aromatic Substitution ◽  
Spin Distribution ◽  
Intermediate Radical ◽  
High Level

The photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction of methanol, 7-methyl-3-methylene-1,6-octadiene ( β-myrcene, 1), and 1,4-dicyanobenzene yields five 1:1:1 adducts:cis-2-(4-cyanophenyl)-4-(1-methoxy-1-methylethyl)-1-methylenecyclohexane (15), trans-2-(4-cyanophenyl)-4-(1-methoxy-1-methylethyl)-1-methylenecyclohexane (16), 1-(4-cyanophenylmethyl)-4-(1-methoxy-1-methylethyl)cyclohexene (17), 4-[4-methoxy-3,3-dimethylcyclohex-(E)-1-ylidenyl]methylbenzonitrile (18), and 4-(1-vinyl-4-trans-methoxy-3,3-dimethylcyclohexyl)benzonitrile (19). All of these adducts are cyclic; variation in the product ratio as a function of methanol concentration indicates cyclization is occurring, 1,6-endo, with both the initially formed radical cation and with the intermediate β-alkoxyalkyl radicals. Evidence based upon comparison of the ionization and oxidation potential of β-myrcene with model alkenes and with conjugated dienes indicates the initial electron transfer involves the trisubstituted mono alkene moiety; the diene moiety, mono-substituted at a nodal position, has a higher oxidation potential. High-level ab initio molecular orbital calculations (MP2/6-31G*//HF/6-31G*) provide useful information regarding the nature (relative energies and charge and spin distribution) of the intermediate radical cations, which supports the proposed reaction mechanism. Key words: photoinduced electron transfer, radicals, radical cations, β-myrcene, cyclization.

Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 6: methanol, nonconjugated dienes, and 1,4-dicyanobenzene

1994 ◽  
Vol 72 (2) ◽  
pp. 415-429 ◽  
Author(s):  
Donald R. Arnold ◽  
Kimberly A. McManus ◽  
Xinyao Du
Keyword(s):  
Electron Transfer ◽  
Double Bond ◽  
Radical Cation ◽  
Oxidation Potential ◽  
Aromatic Substitution ◽  
Double Bonds ◽  
Excited Singlet ◽  
Reaction Conditions ◽  
Methanol Solutions ◽  
Cyclic Adducts

Irradiation, through Pyrex, of an acetonitrile–methanol (3:1) solution of 1,4-dicyanobenzene (1) and 1,5-hexadiene (9) leads to formation of ortho and meta cyclic adducts (13–16) arising from the intermediate exciplex. There was no evidence for interaction between the two double bonds of this nonconjugated diene. The oxidation potential of 9 is high enough (> 3 V vs. sce) to preclude single electron transfer (SET); no photo-NOCAS products are formed. Similar irradiation of acetonitrile–methanol solutions of 1 and 2-methyl-1,5-hexadiene (10) does yield a photo-NOCAS product (17); reaction occurs only on the more heavily substituted double bond. The additional substitution on the double bond lowers the oxidation potential (2.70 V vs. sce) of this diene to the point where SET from 10 to the excited singlet state of 1 can occur. In this case, no cycloaddition products are formed; the exciplex is quenched by electron transfer. There was no evidence for interaction between the two double bonds of the initially formed radical cation 10+•, or between the terminal double bond and the β-alkoxyalkyl radical of the intermediate leading to the photo-NOCAS product. The photo-NOCAS product (19) was also formed when 2,5-dimethyl-1,5-hexadiene (11) was subjected to these reaction conditions. In this case, when biphenyl (4) was added as a codonor, in addition to the photo-NOCAS product, products (21cis and trans) resulting from cyclization of the initially formed acyclic radical cation 11+• to give the 1,4-dimethylcyclohexane-1,4-diyl radical cation were also observed. This 1,6-endo, endo cyclization of 11+• must be rapid enough to compete with reaction with methanol. There was no evidence for cyclization (neither 1,4-exo nor 1,5-endo) of the intermediate β-alkoxyalkyl radical. When the radical cation of 2,5-dimethyl-1,4-hexadiene (12+•) is generated under these reaction conditions, photo-NOCAS products 22 and 23 are formed at the more heavily substituted double bond, along with the conjugated tautomer 2,5-dimethyl-2,4-hexadiene (24). The mechanisms for these transformations are discussed.

The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 5: methanol–monoterpenes (α- and β-pinene, tricyclene, and nopol), 1,4-dicyanobenzene

1994 ◽  
Vol 72 (2) ◽  
pp. 403-414 ◽  
Author(s):  
Donald R. Arnold ◽  
Xinyao Du
Keyword(s):  
Radical Cation ◽  
Radical Cations ◽  
Hydroxyl Group ◽  
Ring Cleavage ◽  
Molecular Orbital Calculations ◽  
Aromatic Substitution ◽  
Alkyl Cations ◽  
Alkyl Moiety ◽  
Cyclobutane Ring ◽  
Tertiary Alkyl

The reactivity of the radical cations of α- and β-pinene (8 and 9), tricyclene (18), and nopol (23) has been studied. The radical ions were generated, in acetonitrile–methanol (3:1), by single electron transfer (set) to the singlet excited state of 1,4-di-cyanobenzene (1). Biphenyl (3) was used as a codonor. The cyclobutane rings of the initially formed radical cations of α- and β-pinene (8+• and 9+•) cleave to distonic radical cations that react as tertiary alkyl cations and allylic radicals. The results of ab initio molecular orbital calculations (STO-3G) are consistent with the observation that the positive charge is largely associated with the tertiary alkyl moiety while the spin density is largely distributed over the allylic radical. There was no evidence, experimental or theoretical, indicative of a bonding interaction between the cationic and allylic moieties of these distonic radical cations. The cyclobutane ring cleavage is irreversible. The radical cation of tricyclene (18) also gives 1:1:1 (nucleophile:cyclopropyl:aromatic) adducts. The regio- and stereochemistry of the adducts, and the nucleophile selectivity, are all indicative of nucleophile-assisted cleavage of the radical cation (18+•). The radical cation of nopol (23+•) also cleaves to the distonic radical cation. The cyclobutane ring cleavage must be rapid; intramolecular 1,5-endo cyclization of the hydroxyl group cannot compete.

The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 8: methanol–2-carene, and 1,4-dicyanobenzene

1995 ◽  
Vol 73 (4) ◽  
pp. 522-530 ◽  
Author(s):  
Donald R. Arnold ◽  
Xinyao Du ◽  
Huub J.P. de Lijser
Keyword(s):  
Electron Transfer ◽  
Molecular Orbital ◽  
Radical Cation ◽  
Bond Cleavage ◽  
Radical Reaction ◽  
Molecular Orbital Calculations ◽  
Aromatic Substitution ◽  
Cyanide Ion ◽  
Bond Forming ◽  
Allylic Radical

The structure and reactivity of the radical cation of (+)-2-carene ((1S,6R)-3,7,7-trimethyl-cis-bicyclo[4.1.0]hept-2-ene (3)) have been studied. The radical cation was generated by photoinduced single electron transfer to the first electronically excited singlet state of 1,4-dicyanobenzene in acetonitrile–methanol (3:1). The 1:1:1 (methanol:2-carene:1,4-dicyanobenzene) adducts were formed: trans-3-(4-cyanophenyl)-4-(1-methoxy-1-methylethyl)-1-methylcyclohexene(14), and cis- (15) and trans-3-(4-cyanophenyl)-6-(1-methoxy-1-methylethyl)-3-methylcyclohexene (16) in a combined yield of 80%. The efficiency of the reaction and the yield of products were increased by the addition of biphenyl, serving as a codonor. These photo-NOCAS adducts formally result from cleavage of the three-membered ring of the 2-carene radical cation, at the C1—C7 bond, forming the tertiary carbocation and allylic radical. Reaction of the cation with methanol and coupling of the allylic radical with the 1,4-dicyanobenzene radical anion at the ipso position, followed by loss of cyanide ion, completes the sequence. There was no evidence for cleavage of the C1—C6 bond under these conditions; however, when the irradiation was carried out in acetonitrile (no methanol) the (+)-2-carene was partially racemized. Racemization is indicative of C1—C6 bond cleavage. The results of abinitio molecular orbital calculations (STO-3G) provide insight into the extent of C1—C7 bond cleavage in the radical cation. The calculated spin and charge distribution, on the 2-carene radical cation global minimum (3a+•), is consistent with the observed regiospecificity of adduct formation. Keywords: photoinduced electron transfer, radical ions, molecular orbital calculations, bond cleavage, 2-carene.

Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction, Part 12. Factors controlling the regiochemistry of the reaction with alcohol as the nucleophile

1996 ◽  
Vol 74 (11) ◽  
pp. 2143-2166 ◽  
Author(s):  
Donald R. Arnold ◽  
Mary S. W. Chan ◽  
Kimberly A. McManus
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Radical Cations ◽  
Major Product ◽  
Convincing Evidence ◽  
Molecular Orbital Calculations ◽  
Aromatic Substitution ◽  
Intermediate Radical ◽  
High Level ◽  
Allylic Radical

The photo-NOCAS reaction that combines methanol, serving as the nucleophile, and the radical cation of 4-methyl-1,3-pentadiene (14+•), substituting on the 1,4-dicyanobenzene radical anion (1−•), yields (E)-1-(4-cyanophenyl)-4-methoxy-4-methyl-2-pentene (15) as the major product. This regioisomer arises from bonding of methanol to C-4, the more heavily alkyl-substituted carbon of the diene, giving the less alkyl-substituted allylic radical. All previous examples of the photo-NOCAS reaction have yielded major adduct(s) having regiochemistry consistent with the anti-Markovnikov rule; the more heavily substituted (more stable?) β-alkoxyalkyl radical was the predominant intermediate. Empirically derived heats of formation and high-level ab initio molecular orbital calculations (MP2/6-31G*//HF/6-31G*) provide convincing evidence that of the two alternative allylic radicals, generated upon addition of methanol to 14+•, that which has the more alkyl substituted allylic radical moiety is, in fact, not the more stable. Of course, the total structure of the intermediate must be considered; the stabilizing effect of alkyl substitution on the carbon next to the oxygen of the ether moiety cannot be ignored. Ab initio molecular orbital calculations (MP2/6-31G*//HF/6-31G*) are reported for the radical cations of 2-methylpropene (2+•), 2-methyl-2-butene (6+•), 2-methyl-1,3-butadiene (9+•), 4-methyl-1,3-pentadiene (14+•), and 2,4-dimethyl-1,3-pentadiene (18+•) Calculations were also carried out on possible intermediates (bridged radical cations, distonic radical cations, and β-alkoxyalkyl radicals) involved upon reaction of these radical cations with methanol. Results of these calculations provide a basis for explaining/predicting the regiochemistry of the photo-NOCAS reaction involving methanol as the nucleophile: the major adduct(s) result(s) from attachment of methanol to that end of the alkene or diene which gives rise to the more stable intermediate radical. The more stable radical is not necessarily the more heavily alkyl substituted. Key words: photoinduced electron transfer, radicals, radical cations, ab initio molecular orbital calculations.

Radiation Effects on Hollandite Ceramics developed for Radioactive Cesium Immobilization

2003 ◽  
Vol 792 ◽  
Author(s):  
V. Aubin ◽  
D. Caurant ◽  
D. Gourier ◽  
N. Baffier ◽  
S. Esnouf ◽  
...  
Keyword(s):  
Radiation Effects ◽  
Liquid Waste ◽  
Fission Products ◽  
Radioactive Cesium ◽  
Radioactive Liquid Waste ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Γ Radiation ◽  
The Stability ◽  
High Level

ABSTRACTProgress on separating the long-lived fission products from the high level radioactive liquid waste (HLW) has led to the development of specific host matrices, notably for the immobilization of cesium. Hollandite (nominally BaAl2Ti6O16), one of the main phases constituting Synroc, receives renewed interest as specific Cs-host wasteform. The radioactive cesium isotopes consist of short-lived Cs and Cs of high activities and Cs with long lifetime, all decaying according to Cs+→Ba2++e- (β) + γ. Therefore, Cs-host forms must be both heat and (β,γ)-radiation resistant. The purpose of this study is to estimate the stability of single phase hollandite under external β and γ radiation, simulating the decay of Cs. A hollandite ceramic of simple composition (Ba1.16Al2.32Ti5.68O16) was essentially irradiated by 1 and 2.5 MeV electrons with different fluences to simulate the β particles emitted by cesium. The generation of point defects was then followed by Electron Paramagnetic Resonance (EPR). All these electron irradiations generated defects of the same nature (oxygen centers and Ti3+ ions) but in different proportions varying with electron energy and fluence. The annealing of irradiated samples lead to the disappearance of the latter defects but gave rise to two other types of defects (aggregates of light elements and titanyl ions). It is necessary to heat at relatively high temperature (T=800°C) to recover an EPR spectrum similar to that of the pristine material. The stability of hollandite phase under radioactive cesium irradiation during the waste storage is discussed.

scholarly journals Computing the Exact Number of Similarity Classes in the Longest Edge Bisection of Tetrahedra

Mathematics ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 1447
Author(s):  
Jose P. Suárez ◽  
Agustín Trujillo ◽  
Tania Moreno
Keyword(s):  
Data Structure ◽  
Stability Condition ◽  
Open Problem ◽  
Integer Arithmetic ◽  
Exact Number ◽  
Similarity Class ◽  
The Stability ◽  
High Level ◽  
The Cost

Showing whether the longest-edge (LE) bisection of tetrahedra meshes degenerates the stability condition or not is still an open problem. Some reasons, in part, are due to the cost for achieving the computation of similarity classes of millions of tetrahedra. We prove the existence of tetrahedra where the LE bisection introduces, at most, 37 similarity classes. This family of new tetrahedra was roughly pointed out by Adler in 1983. However, as far as we know, there has been no evidence confirming its existence. We also introduce a new data structure and algorithm for computing the number of similarity tetrahedral classes based on integer arithmetic, storing only the square of edges. The algorithm lets us perform compact and efficient high-level similarity class computations with a cost that is only dependent on the number of similarity classes.

Features of pubertal patients with schizophrenia neurocognitive profile

2017 ◽  
Vol 41 (S1) ◽  
pp. S430-S431
Author(s):  
Y. Barylnik ◽  
S. Pakhomova ◽  
D. Samoylova ◽  
J. Abrosimova ◽  
E. Kolesnichenko ◽  
...  
Keyword(s):  
Stability Index ◽  
Neurocognitive Disorders ◽  
Motor Speed ◽  
Structuring Element ◽  
Test Part ◽  
Psychic Disorders ◽  
Competing Interest ◽  
Neurocognitive Profile ◽  
The Stability ◽  
High Level

Identifying the patterns of neurocognitive disorders in pubertal schizophrenia is actual.MethodsBenton Test of visual retention, methods of forward and reverse bills, Bourdon correction sample, Wechsler's subtests (subtest 11 – “Encryption”, subtest 12 – “Labyrinths” 1, 2, 3, 4, 5), Trail Creating a Test Part A.ResultsAll patients were divided into 3 groups. The first group (schizophrenia) and second group (other psychic disorders) showed the worst results than healthy subjects. Qualitative analysis of the “Benton Test” results showed similar variations of difficulty and types of errors in the subjects of the first and second groups – ignoring the number of the figure sides, as well as difficulties in the structuring element of the image corners. The “Methods of forward and reverse bills” demonstrated the fatigue and attention instability. “Bourdon test” showed a high level of the stability index (K = 0.09). Wechsler's subtest “Encryption B” obtained poor results, indicating a pathological decrease in visual-motor speed. During the subtest “Labyrinths 1, 2, 3, 4, 5” the subjects of first and second groups exceeded the allowable time limit, but the first group of schizophrenia patients allowed more blunders during pubertal study (ignored the walls of the maze, torn pencil despite the given instructions). The test groups 1 and 2 while passing “Trail Creating a Test Part A” have shown good results – job data did not cause difficulties and carried out in accordance with the specified instructions.ConclusionsNeurocognitive disorders allow to confirm the presence of morphological and functional brain changes when endogenous mental illness occurs.Disclosure of interestThe authors have not supplied their declaration of competing interest.

THE ROLE OF ACCOUNTING AND CONTROL IN THE MANAGEMENT OF ECONOMIC SECURITY OF AN ORGANIZATION

2021 ◽  
Vol 7 (2) ◽  
pp. 165-178
Author(s):  
Nicolay T. Labyntsev ◽  
Lyubov F. SHILOVA ◽  
Ocsana V. Chukhrova
Keyword(s):  
Economic Security ◽  
Accounting Profession ◽  
Economic Management ◽  
Economic Interests ◽  
Doing Business ◽  
The Subject ◽  
The Stability ◽  
High Level ◽  
And Control

This article revises the mission and the name of the accounting profession in the context of strengthening the economic security of enterprises under the conditions of digitalization of the economy. The authors note that in the contemporary conditions of economic management, enterprises should form and ensure the functioning of the economic security of the enterprise at the proper level. The necessity of in-depth research of economic security at microlevel was considered, the factors influencing the stability of the enterprise were highlighted. High level of economic security of the subject of management consists in guaranteeing him maximum effective and stable functioning now and in future. Subjects of economic security were individual enterprises, and objects — their economic interests. The main goals of ensuring economic security of the enterprise in the part of accounting were singled out, the tasks of accounting policy, aimed at ensuring economic security, were determined. The prospects of the accounting profession in the process of ensuring economic security and reliable safe presentation of the results of doing business in reporting are substantiated. The study contains proposals on the revision of requirements for the qualifications of accountants in order to emphasize their activities aimed at strengthening the economic security of the enterprise.

Sign in / Sign up

Export Citation Format

Share Document