4,6-二甲基-2-取代嘧啶的合成

采用改进的合成方法以乙酰丙酮分别与胍、硫脲、脲反应合成了三种2位杂原子取代的嘧啶类化合物,收率83．8％-98．6％,其结构经1^H NMR,IR和MS表征。     

Synthesis and Characterization of Novel Organosoluble Methyl Substituted Poly(aryl Ether Ketone)s Containing Sulfone Linkage

Several new methyl substituted poly(aryl ether ketone)s containing sulfone linkage with inherent viscosities of 0.62–0.84 dL/g have been prepared from 4,4′‐bis(2‐methylphenoxy)diphenylsulfone and 4,4′‐bis(3‐methylphenoxy)diphenylsulfone with terephthaloyl chloride and isophthaloyl chloride by electrophilic Friedel‐Crafts acylation in the presence of DMF with anhydrous AlCl₃ as a catalyst in 1,2‐dichloroethane, respectively. These polymers having weight‐average molecular weight in the range of 71,000–49,000 are all amorphous and show high glass transition temperatures ranging from 167 °C to 191 °C, excellent thermal stability at temperatures over 400 °C in air or nitrogen, high char yields of 51–58% in nitrogen and good solubility in CHCl₃ and polar solvents such as DMF, DMSO and NMP at room temperature.     

取代基对二硅炔及其异构体的结构与稳定性的影响

用从头算量子化学方法,在6-31G^*^*水平上对取代二硅炔及其异构体HYSi~2和Y~2Si~2(Y=F,Cl,Br,Li)的构型和稳定性进行了理论研究,详细讨论了取代基对各种异构体,尤其是对Si-SI键稳定性的影响。研究结果表明,亚硅基硅烯和双桥构型能量最低,是各种取代二硅炔及异构体的实验上可探测的构型;而经典的线型二硅炔构型能量高,是不稳定的。     

Reaction of ethyl bromoacetate with substituted naphthoate ions

Rate constants for the reaction of ethyl bromoacetate with three series of substituted naphthoate ions have been measured in an acetone-water mixture (90% v/v). Using σ _p values rate constants at 30^o correlate well with the Hammett equation yielding ρ=−0.54, −0.19 and −0.25 for (4,1−), (6,1−) and (6,2−) series, respectively. Comparison of these ρ values with those of the reaction of phenacyl bromide reveals the failure of the reactivity-selectivity principle RSP in these reactions. Failure of RSP has been explained in terms of isoselective temperature.     

Enthalpic interaction coefficients of formamides dissolved in N,N-dimethylformamide

Enthalpies of dilution of formamide, N-methylformamide, N-ethylformamide, N-propylformamide, N-butylformamide, N-pentylformamide, N,N-diethyl-formamide, N,N-dipropylformamide, N,N-dibutylformamide, and N,N-dipentyl-formamide dissolved in N,N-dimethylformamide as solvent have been measured calorimetrically at 25°C. The results are interpreted in terms of the McMillan-Mayer theory. Enthalpic interaction parameters are obtained for pairs, triplets, and in some cases, quadruplets of solute molecules. In general, the enthalpic pair interaction coefficients are negative, whereas the triplet coefficients are positive. The interaction enthalpies are positive only for N-methylformamide and formamide. The magnitudes of the enthalpic pair and triplet interaction coefficients increase with increasing number of C atoms in the N-alkyl groups. The results for the formamides presented in this paper are compared with those for corresponding acetamides published earlier. Although the trends are comparable, distinct differences are observed. The contribution of the -CH₃ group at the CO side of the dialkylacetamides to the enthalpic interaction coefficients appears to be negligible. The same is true for -CH₂ groups at the NH side of a number of amides and related compounds. The enthalpic pair interaction coefficients of the mono-N-alkylsubstituted formamides show a shift of about 100 J-kg-mol^–2 as compared with isomeric N-alkylacetamides. This is discussed in terms of the difference in proton donating and accepting ability of several types of amide molecules. It is concluded that substitution effects should be incorporated in additivity models for these type of systems.     

Interactions between terminally substituted amino acids in an aqueous and a non-aqueous environment. Enthalpic interaction coefficients in water and in N,N-dimethylformamide at 25°C

Enthalpies of dilution of the N-acetyl amides of glycine, L-alanine, L-valine, L-leucine, and L-phenylalanine, dissolved in N,N-dimethylformamide (DMF) as a solvent have been measured at 25°C. The results obtained have been analyzed to give the enthalpic interaction (or virial) coefficients of the solutes and these are compared with information previously obtained in aqueous systems. There are marked differences in the interaction properties in the two solvents and, while the additivity approach of Savage and Wood is applicable to the solutes in water it is not suitable for representing the interactions in DMF. A correlation is presented between the enthalpic second virial coefficients in DMF and the propensity of side-chains to be in proximity in globular proteins.     

Four-Step Spin Crossover in a New Cyano-Bridged Iron-Silver Coordination Polymer

Spin-crossover complexes with multistep transitions attract much attention due to their potential applications as multi-switches and for data storage. A four-step spin crossover is observed in the new iron(II)-based cyanometallic guest-free framework compound Fe(2-ethoxypyrazine)₂{Ag(CN)₂}₂ during the transition from the low-spin to the high-spin state. A reverse process occurs in three steps. Crystallographic studies reveal an associated stepwise evolution of the crystal structures. Multiple transitions in the reported complex originate from distinct Fe^II sites which exist due to the packing of the ligand with a bulky substituent.     

2-羟基-4-(1′-甲庚氧基)苯烷酮肟的合成

具有邻位羟基的酮肟化合物(1)作为过渡金属螯合剂已在铜的萃取-电积工艺中得到广泛应用,如:LIX 64N(1a),LIX84(1b)及LIX 860(1c)。从萃取动力学行为来衡     

苯胺类化合物的电化学氧化及随后化学反应

利用循环伏安法研究了二取代对苯二胺(1),四取代对苯二胺(2)和二取代氨基酚(3)三类化合物以及它们的衍生物的电化学行为及其氧化产物的随后不可逆脱氨反应。 1类化合物在任何pH下的电化学氧化均为一步双电子转移反应,2类化合物为二步单电子转移反应;3类化合物在酸性和中性范围为一步双电子氧化在碱性溶液中为二步单电子转移反应。文中定量求算了不可逆随后化学反应的表观水解速率常数k_f,并进行了讨论。     

钒钼磷杂多酸催化苯直接羟化为苯酚的动力学研究

以钒钼磷杂多酸作为催化剂,用紫外可见分光光度法研究了过氧化氢直接将苯氧化羟基化为苯酚反应的动力学行为。结果表明,该氧化羟化反应速率对底物苯、氧化剂和催化剂都是一级反应,反应的活化能为57.73kJ.mol-1。本文推测了杂多酸配合物催化苯氧化羟化为苯酚反应的过程,建立了该反应动力学数学模型,模型很好地解释了实验结果。