胺丶醇丶醚类化合物气相碱性的CNDO/2计算

The gas-phase basicities of compounds can be measured by their proton affinities. In this paper we he calculated the gas-phase basicities of about seventy compounds containing N or O by means of the method CNDO/2. For the alkylamines, alcohols, ethers and carbonyl compounds, computational results agree qualitatively with the experimental values. The sequences of gas-phase basicities for the series of these compounds are as follows: Et2NH>Me3N>t-BuNH2>Me2NH>i-PrNH2>n-BuNH2>n-PrNH2>EtNH2>MeNH2>NH3; Et2O>EtOMe>t-BuOH>Me2O>i-PrOH>n-BuOH>n-PrOH>EtOH>MeOH>H2O; n-PrCHO>EtCHO>MeCHO>HCHO; n-BuCO2H>n-PrCO2H>EtCO2H>MeCO2H>HCO2H; HCO2Bu-n>HCO2Pr-N>HCO2Et>HCO2Me>HCO2H Obviously, alkyl substitution plays a role to increase the gas-phase basicities. The squence of increasing effectiveness is t-Bu>i-Pr>n-Bu>n-Pr>Et>Me For the amines containing heteroatoms investigated here, the gas-phase basicities have the following order repectively: CH3NH2>NH2NH2>NH2OH>NH2F>NHF2>NF3 The gas-phase basicities of these compounds change regularly with various substitutents. For the aliphatic compounds, the gas-phase basicity increases with thosizo and the degree of branching of the alkyl groups. For the amines containing heteroatoms, the gas-phase basicity decreases with increasing of the electro-negativity of the substitutent. For the relationship between the gas-phase basksity and the charge distribution and the ionization potentials, the conclusions are as follows: (1) The gas-phase basicities of the homologous compounds are proportional to the electron density of the atom N or O, but those of Rn NH3-n and Rn OH2-n are inversely proportional to the electron denisty of atom N or O. This shows that the base strength of the molecule cannot be determined solely by the electron density of the individual atom. (2) In the protonation reaction the alkyl groups spread the charges from the charged center. This effect enables protonated cations to become more stable because of the charge distribution av     

A CNDO/2 calculation on stilbene

The equilibrium conformations of trans- and cis-stilbene and the rotational barrier between the two isomers were calculated using the CNDO/2 method. The results for the equilibrium angles and distances are in good agreement with experimental data. However, according to the calculations the phenyl rings would have a nearly free rotation which is only limited by steric hindrance. This result obviously deviates from the current view. The results are discussed in relation to previous theoretical and experimental evidence.

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Zusammenfassung Die Gleichgewichtskonformation von trans- und cis-Stilben und die Rotationsbarriere zwischen zwei Isomeren wurde nach der CNDO/2-Methode berechnet. Die Ergebnisse in bezug auf die Geometrie stimmen mit experimentellen Daten gut überein, die Rotationsbarriere für die Drehung der Phenylringe dagegen ist praktisch Null.

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Résumé La méthode CNDO/2 a été employée pour calculer les conformations d'équilibre du trans- et du cis-stilbène ainsi que la barrière de rotation entre ces deux isomères. Angles d'équilibre et distances calculés sont en bon accord avec les données expérimentales. Cependant les calculs indiquent que les cycles phényles devraient posséder une rotation libre soumise seulement à l'empêchement stérique. Ce résultat s'écarte de l'opinion courante. Les résultats sont discutés en relation avec les données théoriques et expérimentales antérieures.

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This work was supported by grant No 2741-4 from The Swedish Natural Science Research Council and grant No 69-927/U 697 from The Swedish Board for Technical Development.     

胺、醇和醚类化合物电离能的估算

脂肪族胺、醇、醚、硫醇和硫醚的第一电离能Ip与N、O、S原子的电负性X~Z^O、分子中N、O、S原子的部分电荷q~z以及烷基的极化效应指数PEI的关系可以表示为:Ip(eV)=4.4851+3.0727X~Z~O+7.1702q~z-1.3949∑PEI上式较好地表达了脂肪族胺、醇、醚、硫醇和硫醚的第一电离能变化的共同规律。     

2-取代吡啶衍生物的CNDO/2计算和分子光谱研究

本文用CNDO/2方法计算了吡啶及其2-取代衍生物,测了其紫外光谱.通过红外,紫外光谱和量子化学计算的综合分析,确定2-吡啶酮与2-羟基吡啶是互变异构体,并推断2-氨基吡啶的互变异构体存在,从而很好地得到了此系列紫外光谱的线性规律.     

胺、醇、醚类化合物电离能的自相关拓扑研究

原子的染色序数 fi 定义为 :fi=gi·xi,式中 gi 为原子i在分子中的序数 ,xi 为其染色系数 .基于fi 建立改进的原子序数自相关拓扑指数mF ,其中的1F对烷烃及其衍生物具有良好的结构选择性 .使用第一电离能 (Ip)与0 F ,1F的数量关系模型对 32种脂肪族胺、醇、醚进行估算、预测 ,结果令人满意     

Comparison of quantum mechanical and experimental gas-phase basicities of amines and alcohols

A comparison was made between the experimental and B3LYP relative gas-phase basicities and proton affinities of a series of 9 amine, 3 alcohol, and 3 alkanolamine molecules. While agreement is good for most of the species studied, it is poor for the alkanolamines and 1,2-ethanediol. A series of calculations were undertaken at the B3LYP and MP2 levels using various basis sets to see if the uncertainties in the calculations can account for the discrepancies. The results suggest that this is unlikely and that the theoretical values are likely to be reasonably accurate. Calculations are also presented for the dimer formation energies of alkanolamine molecules, diamine molecules, and 1,2-ethanediol. These calculations suggest that all of these species can form proton-bound dimers. The alkanolamines and 1,2-ethanediol also appear to have relatively high formation energies for neutral dimers.     

CNDO/2 calculation of prototropic rearrangement in cyclopentadiene

A self-consistent procedure has been worked out for the optimisation of geometrical parameters of ground and transition states of molecular systems and chemical reactions. For cyclopentadiene molecule, the CNDO/2 method is used to calculate a number of the geometrical configurations which lie at the reaction co-ordinates corresponding to possible channels of the proton migration.     

A CNDO/2 calculation on a complex between ethylene and chlorine

CNDO/2 calculations have been carried out for an ethylene chlorine complex, with the halogen orthogonal or parallel to the C-C bond. For comparison similar calculations were also carried out for ethylene and fluorine. The results are compared to estimates from experiments on related complexes and from Mulliken's resonance theory. It is concluded that the CNDO/2 calculations grossly overestimate the ethylene-chlorine interaction in particular if d-orbitals on chlorine are included in the AO-basis. The explanation for this may be the too high d-orbital exponent used here and the wrong asymptotic behaviour of the Slater orbitals.

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Zusammenfassung Es werden CNDO/2-Rechnungen für zwei Konformationen eines Äthylen-Chlor-Komplexes und eines Fluor-Analogens berichtet und die Resultate mit der Resonanztheorie von Mulliken und mit experimentellen Daten verglichen. Es ergibt sich, daß bei CNDO/2-Rechnungen die ChlorÄthylen-Wechselwirkung stark überschätzt wird, insbesondere, wenn d-Orbitale eingeschlossen werden. Letzteres könnte auch an einem großen Exponenten bei diesen Funktionen oder am falschen asymptotischen Verlauf von Slater-Funktionen liegen.

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Résumé Calculs CNDO/2 pour un complexe ethylène-chlore avec l'halogène orthogonal ou parallèle à la liaison C-C. A titre de comparaison des calculs analogues ont été aussi effectués pour l'éthylène et le fluor. Les résultats sont comparés à des estimations expérimentales sur des complexes voisins et à des estimations provenant de la théorie de la résonance de Mulliken. La conclusion est que les calculs CNDO/2 surestiment beaucoup l'interaction éthylène-chlore, en particulier lorsque l'on inclut des orbitales d dans la base des orbitales atomiques. La raison peut s'en trouver dans les exposants trop élevés des orbitales d et dans le mauvais comportement asymptotique des orbitales de Slater.

     

A CNDO/2 calculation of a rearrangement in cyclopentadienylsilane

The ground state geometry of cyclopentadienylsilane and the transition state geometry for SiH₃ group migration have been calculated by the CNDO technique, a semi-empirical version of the LCAO MO SCF approach.     

Kinetics of the gas-phase reactions of the oh radical with selected glycol ethers,glycols, and alcohols

Using a relative rate method, rate constants have been measured for the gas-phase reactions of the OH radical with 1-hexanol, 1-methoxy-2-propanol, 2-butoxyethanol, 1,2-ethanediol, and 1,2-propanediol at 296±2 K, of (in units of 10⁻¹² cm³ molecule⁻¹ s⁻¹): 15.8±3.5; 20.9±3.1; 29.4±4.3; 14.7±2.6; and 21.5±4.0, respectively, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. These OH radical reaction rate constants are higher than certain of the literature values, by up to a factor of 2. Rate constants were also measured for the reactions of 1-methoxy-2-propanol and 2-butoxyethanol with NO₃ radicals and O₃, with respective NO₃ radical and O₃ reaction rate constants (in cm³ molecule⁻¹ s⁻¹ units) of: 1-methoxy-2-propanol, (1.7±0.7)×10⁻¹⁵, and <1.1×10⁻¹⁹; and 2-butoxyethanol, (3.0±1.2)×10⁻¹⁵, and <1.1×10⁻¹⁹. The dominant tropospheric loss process for the alcohols, glycols, and glycol ethers studied here is calculated to be by reaction with the OH radical, with lifetimes of 0.4–0.8 day for a 24 h average OH radical concentration of 1.0×10⁶ molecule cm⁻³. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 533–540, 1998     

CNDO/2 molecular orbital calculations on the complexes formed between dimethylberyllium and aliphatic amines

A systematic CNDO/2 study has been carried out on the molecular complexes formed between dimethylberyllium and aliphatic amines. It has shown that the calculated molecular properties of these complexes, viz. the interaction energy, amount of charge transferred and the enhancement of the dipole moment are related to the ionization potential of the amine. The results are discussed in terms of the Mulliken's charge transfer theory.     

Experimental gas-phase basicity scale of superbasic phosphazenes

Seventeen superbasic phosphazenes and two Verkade's bases were used to supplement and extend the experimental gas-phase basicity scale in the superbasic region. For 19 strong bases the gas-phase basicity values (GB) were determined for the first time. Among them are such well-known bases as BEMP (1071.2 kJ/mol), Verkade's Me-substituted base (1083.8 kJ/mol), Et-N=P(NMe2)2-N=P(NMe2)3 (Et-P2 phosphazene, 1106.9 kJ/mol), and t-Bu-N=P(NMe2)3 (t-Bu-P1 phosphazene, 1058.0 kJ/mol). For the first time experimental GB values were determined for P2 phosphazenes. Together with our previous results self-consistent experimental gas-phase basicity scale between 1020 and 1107 kJ/mol is now established. This way an important region of the gas-phase basicity scale, which was earlier dominated by metal hydroxide bases, is now covered also with organic bases making it more accessible for further studies. The GB values for several superbases were calculated using density functional theory at the B3LYP/6-311+G** level. For the phosphazene family the standard deviation of the correlation between the experimental and theoretical values was 6.5 kJ/mol.     

诱导效应描述符与胺、醇、醚类化合物电离能的关系

提出了诱导效应均衡原理,在此基础上导出了一个新的诱导效应描述符,并给出了一套新的诱导效应参数(IEP).结合原子序数自相关拓扑指数0F和1F,研究了胺、醇、醚类化合物第一电离能(IP)的定量构效关系,用该式预测了32种胺、醇、醚类化合物的第一电离能,平均绝对误差仅为0.044 5 eV,预测值与实验值十分吻合,优于文献报道的方法.     

Saccharin sulfonic acid catalyzed N-Boc protection of amines and formation of tert-butyl ethers from alcohols

Saccharin sulfonic acid (SaSA), as a stable reagent is easily prepared by the reaction of saccharin with neat chlorosulfonic acid at room temperature. This compound is able to catalyze conversion of amines to their corresponding N-Boc protected amines with (Boc)₂O. Alcohols were also converted to their corresponding tert-butyl ethers. All reactions took place under mild conditions giving the desired products in good to high yields.     

CNDO/2 molecular orbital calculations on the complexes formed between methyllithium and trimethylaluminium with aliphatic amines

Mono-(I), bis-(II), and tris-(triferrocenylphosphine)iron carbonyls (III) were obtained photochemically or thermally in high yields. The photochemical reaction of triferrocenylphosphine with iron pentacarbonyl was found to proceed only at elevated temperature, and it was discovered that I, first formed almost quantitatively, is converted to III by a disproportionation process. Complex II is not formed as an intermediate, notwithstanding the fact that II can be obtained by photochemically induced disproportion, as well as by thermally initiated substitution, from I as starting material. Several aspects of the reaction were explored, and a mechanism is suggested to account for the observed behavior. The product of the thermally initiated reaction of triferrocenylphosphine with butadieneiron tricarbonyl was characterized as a tris(phosphine)iron dicarbonyl (IV), structurally different from III. An examination of carbonyl stretching bands indicated that I and II are very probably trigonal bipyramidal in configuration with the phosphine ligand axially disposed. Consideration is given to possible structural configurations for III and IV.     

On molecular polarizability: 3. Relationship to the ionization potential of haloalkanes, amines, alcohols, and ethers

The relationship between the ionization potential and the parameters molecular electronegativity and molecular polarizability for haloalkanes, amines, alcohols, and ethers was investigated. There is no good linear correlation between the ionization potential Ip and molecular electronegativity chi(eq) alone for these compounds. Ip can be modeled well with three parameters: chi(eq), polarizability effect index (PEI) of an alkyl group, and atomic polarizability (P). Further, a single expression for predicting the Ip values of aldehydes, esters, nitriles, and carboxylic acids was developed: Ip(Rz)(eV) = Ip(MeZ) + 1.4544delta chi(eq) - 1.6435delta sigmaPEI(Ri). Here Ip(MeZ) is the experimental ionization potential of monosubstituted methane MeZ. Delta chi(eq) and delta sigmaPEI(Ri) are the difference in the molecular electronegativity and the difference in the polarizability effect index of alkyl groups attached to the functional group Z between molecules MeZ and RZ, respectively.