Acta chemica Scandinavica (Copenhagen, Denmark : 1989)最新文献_第3页

Metaquat, a paraquat isomer isolated from an arrow poison. 百草枯，一种从箭毒中分离出来的百草枯异构体。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1998-03-01 DOI: 10.3891/acta.chem.scand.52-0372

T I Sølling

引用次数: 4

Radical and polar reactivity of radical ions in solution. A new look at an old problem. 自由基离子在溶液中的自由基和极性反应性。对老问题的新看法。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1998-02-01 DOI: 10.3891/acta.chem.scand.52-0145

V D Parker

{"title":"Radical and polar reactivity of radical ions in solution. A new look at an old problem.","authors":"V D Parker","doi":"10.3891/acta.chem.scand.52-0145","DOIUrl":"10.3891/acta.chem.scand.52-0145","url":null,"abstract":"It is proposed that both polar and radical reactions should be considered when discussing radical ion reactivity. The fact that only the polar reactivity has dominated previous discussions is pointed out. It is argued that if the configuration mixing model is applicable for the estimation of radical cation-nucleophile (or cation-nucleophile) combination reaction barriers, the theory should also explain the reactivity of the proton toward anionic nucleophiles. The model severely overestimates reaction barriers for the latter reactions. The discussion is centered around the following hypothesis: In the absence of severe steric effects, the reactivity of radical ions, especially evident in the reactions with radicals (for example very few radical cations react with dioxygen at measurable rates), is dominated by the degree of coupling between charge and radical centers. Evidence from the literature supporting the hypothesis is presented for a number of different classes of radical ion reactions. Further work to test the validity of the hypothesis is proposed for many of the reaction types. Triarylmethyl radicals and carbenium ions are suggested as models to which the radical and polar reactivities of 9,10-diarylanthracene radical cations may be compared. It is concluded that the radical cation/carbenium ion comparison (for the reaction with acetate ion) would show similar reactivities while the radical cation/free radical comparison (for the reaction with dioxygen) would fail, since no reaction at all would be observed with the radical cation while the free radical reacts rapidly.","PeriodicalId":76966,"journal":{"name":"Acta chemica Scandinavica (Copenhagen, Denmark : 1989)","volume":"52 2","pages":"145-53"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20411868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Radical reactivity of radical ions in solution. Radical-radical and radical-substrate coupling mechanisms. 自由基离子在溶液中的自由基反应性。自由基-自由基和自由基-底物耦合机制。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1998-02-01 DOI: 10.3891/acta.chem.scand.52-0154

V D Parker

{"title":"Radical reactivity of radical ions in solution. Radical-radical and radical-substrate coupling mechanisms.","authors":"V D Parker","doi":"10.3891/acta.chem.scand.52-0154","DOIUrl":"https://doi.org/10.3891/acta.chem.scand.52-0154","url":null,"abstract":"The linear sweep voltammetry response to competitive radical ion-substrate coupling and radical ion dimerization mechanisms was determined by digital simulation. The simulations were carried out to mimic the conditions under which experimental studies had previously shown that the radical ion-substrate coupling mechanism is the preferred reaction pathway. It was observed that in order for the dependence of the peak potential on substrate concentration (delta Ep/delta log CA) to be in the experimentally observed range (36-40 mV/decade) that the relative rate constants for radical ion substrate coupling and radical ion dimerization (ki/kii) must be greater than about 10. It is pointed out that since the reactants, the transition states and the products differ by only a single electron that these competitive reactions represent an ideal test case for the configuration mixing (CM) model. The CM model predicts an electronic reaction barrier for reaction (i) but not for reaction (ii). The difference in standard free energy changes for reactions (i) and (ii) were estimated to be of the order of 7 kcal mol-1 or greater with (ii) being energetically more favorable than (i). It is concluded that the experimental data for the relative rates of reactions (i) and (ii) do not conform to the CM model predictions in the cases discussed. ArH(.+) + ArH-->+ ArH-ArH.(i) ArH(.+) + APH .+ --> + ArH-ArH+(ii).","PeriodicalId":76966,"journal":{"name":"Acta chemica Scandinavica (Copenhagen, Denmark : 1989)","volume":"52 2","pages":"154-9"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20411869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 11

Electrosyntheses from aromatic aldehydes in a flow cell. Part I. The reduction of benzaldehyde. 流动电池中芳香族醛的电合成。第一部分:苯甲醛的还原。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1998-01-01 DOI: 10.3891/acta.chem.scand.52-0023

T Guena, D Pletcher

引用次数: 14

Electrosyntheses from aromatic aldehydes in a flow cell. Part II. The cross-coupling of benzaldehydes to unsymmetrical diols. 流动电池中芳香族醛的电合成。第二部分。苯甲醛与不对称二醇的交叉偶联。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1998-01-01 DOI: 10.3891/acta.chem.scand.52-0032

T Guena, D Pletcher

引用次数: 6

Total synthesis of C31-methyl ketone apocarotenoids. 3. On the structure of hopkinsiaxanthin: first total synthesis of (all-E)-(3S)- and (9Z)-(3S)-7'-apohopkinsiaxanthin. c31 -甲基酮类伪胡萝卜素的总合成。3.hopkinsiaxanthin的结构:首次合成(all-E)-(3S)-和(9Z)-(3S)-7'-apohopkinsiaxanthin。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1997-12-01 DOI: 10.3891/acta.chem.scand.51-1201

J A Haugan, E Lobkovsky, S Liaaen-Jensen

{"title":"Total synthesis of C31-methyl ketone apocarotenoids. 3. On the structure of hopkinsiaxanthin: first total synthesis of (all-E)-(3S)- and (9Z)-(3S)-7'-apohopkinsiaxanthin.","authors":"J A Haugan, E Lobkovsky, S Liaaen-Jensen","doi":"10.3891/acta.chem.scand.51-1201","DOIUrl":"https://doi.org/10.3891/acta.chem.scand.51-1201","url":null,"abstract":"Optically active (all-E)-(3S)-7'-apohopkinsiaxanthin, previously known as F1, and (9Z)-(3S)-7'-apohopkinsiaxanthin have been prepared by total synthesis for the first time in ca. 1% combined overall yield, including two unidentified geometrical isomers, in sixteen linear steps from (4R,6R)-actinol, (2E)-3-methyl-2-penten-4-yn-1-ol, (7-formyl-2-methyl-2,4,6-octatrienyl)triphenylphosphonium bromide, (3-formyl-2-butenyl)triphenylphosphonium bromide and methyllithium, by use of a C15 + C10 + C5 + C1 approach. By an alternative route from (2Z)-5-[((4S)-4-hydroxy-2,6,6-trimethyl-3-oxo-1-cyclohexenyl)-3- methyl-2-penten-4-ynyl]triphenylphosphonium bromide, (7-formyl-2-methyl-2,4,6-octatrienyl)triphenylphosphonium bromide and (2E)-3-methyl-4-oxo-2-pentenal, the same target compounds were obtained in a combined overall yield of > 61%, including four unidentified geometrical isomers, over two steps, by use of a C15 + C16 approach. A hypothetical structure for hopkinsiaxanthin is discussed, based on present and previously reported spectroscopic and chemical data for (all-E)-(3S)- and (9Z)-(3S)-7'-apohopkinsiaxanthin and on data previously reported for hopkinsiaxanthin itself.","PeriodicalId":76966,"journal":{"name":"Acta chemica Scandinavica (Copenhagen, Denmark : 1989)","volume":"51 12","pages":"1201-16"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20316952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Determination of dissociation constants of loop diuretics in acetonitrile-water mixtures. 乙腈-水混合物中环状利尿剂解离常数的测定。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1997-11-01 DOI: 10.3891/acta.chem.scand.51-1078

J Barbosa, D Barrón, S Buti

引用次数: 1

Total synthesis of (+/-)-monomorine I and (+/-)-indolizidine 195B by an aza-[2,3]-Wittig rearrangement of a vinylaziridine. 全合成(+/-)-单分子胺I和(+/-)-吲哚吡啶195B的aza-[2,3]- witig重排。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1997-10-01 DOI: 10.3891/acta.chem.scand.51-1024

P Somfai, T Jarevång, U M Lindström, A Svensson

引用次数: 16

Acid-base behavior of quinolones in aqueous acetonitrile mixtures. 喹诺酮类药物在乙腈水溶液中的酸碱行为。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1997-09-01 DOI: 10.3891/acta.chem.scand.51-0896

V Sanz-Nebot, I Valls, D Barbero, J Barbosa

引用次数: 29

Structural determination of a dimeric side-product accompanying dihydropyrazine preparation. 伴随二氢吡嗪制剂的二聚体副产物的结构测定。

Acta chemica Scandinavica (Copenhagen, Denmark : 1989) Pub Date : 1997-09-01 DOI: 10.3891/acta.chem.scand.51-0938

D Gopal, D Macikenas, L M Sayre, J D Protasiewicz

引用次数: 2