查询词典 aldehydes

After cooking, ketones increase, 3-penten-2-one, 1-penten-3-one and 2-nonanone contributed the good flavor. At the same time, cooking reduced the acids and ringed compounds, which was benifical for the flavor. Although the content of aldehydes didn't change significantly, but the contents of some aldehydes, such as benzaldenyde, heptanal, nonyl aldenhyde lilac aldehyde and 4Z-heptenal, which contributed good flavor to the cooked oyster, increased.Maillard reaction was used to improve the flavor of the flavor product from oyster.

对于生牡蛎，烃类以及1-辛烯-3-醇、4-壬烯醛、2-辛醛等会对风味产生较大的影响；在煮制后的牡蛎中，酮类的数量增加，并大多贡献出美好的风味，其中3-戊烯-2-酮、1-戊烯-3-酮、2-壬酮对煮制牡蛎的风味具有好的作用：煮制会使酸类和带有不良风味的环状化合物的数量减少；醛类的数量和含量在煮制前后虽然没有太大的改变，但是苯甲醛、庚醛、壬醛、丁香醛、4-Z庚烯醛等可以产生良好风味的物质含量增加，贡献了煮制后牡蛎的美好风味。

Master the Keto-Enol tautomerism; reactions of enols:α-H substitution reactions;α-halogenation of aldehydes and ketones;α-bromination of carboxylic acids; acidity ofα-H atoms: enolate ion formation; reactivity of enolate ions; alkylation of enolate ions; mechanism of carbonyl condensation reactions;condensations of aldehydes and ketones: the Aldol reaction; dehydration of Aldol products; the Claisen condensation reaction; the Michael addition.

熟练掌握酮式－烯醇式互变异构；烯醇的反应：α-H的活性；醛酮的α卤代反应；羧酸的α-溴代反应；α-H的酸性：烯醇负离子的形成；烯醇负离子的反应；烯醇负离子的烃基化；羰基化合物的缩合反应机理；醛酮的缩合反应－Aldol缩合；Aldol缩合产物的脱水反应； Cleisen 酯缩合反应；麦克尔加成反应。

For the saturated aromatic aldehydes with malononitrile and barbituric acidit, the reaction was found to proceed very efficiently at room temperature giving excellent yields under ultrasonic irradiation, while for α,β-unsaturated aldehydes as well as p-phthalaldehyde with malononitrile and barbituric acid the reaction also proceeded smoothly at room temperature with good yields.

在超声波辐射下，不仅饱和芳香醛与丙二腈、巴比妥酸的一锅反应在室温下能高收率地进行，而对于α，β-不饱和醛以及二元醛与丙二腈、巴比妥酸的一锅反应也能在室温下顺利进行，获得较高的收率。

In this catalyst system, the Knoevenagel condensations of a series of aromatic aldehydes with malononitrile or ethyl cyanoacetate were programmed and a mechanism was postulated as well. When aromatic aldehydes reacted with ethyl cyanoacetate, the corresponding alkenes proved to be E-isomers by 1H NMR.

在该反应体系中考察了一系列芳香醛和丙二氰、氰基乙酸乙酯的缩合反应，并推测了Knoevenagel缩合反应的机理，芳香醛与氰基乙酸乙酯缩合产物经1H NMR检测为E式烯烃。

The condensation of aromatic aldehydes with active methylene compounds like malononitrile, cyanoacetamide and ethyl cyanoacetate has been found to proceed very efficiently at room temperature giving excellent yields, but the condensation of heteroaromatic,α,β-unsaturated and aliphatic aldehydes with active methylene compounds proceeded smoothly in 50~65℃ with good yields and the reactions of aromatic, aliphatic ketones as well as p-phthalaldehyde with malononitrile also proceeded in 75~85℃ with moderate yields.

芳香醛与活泼亚甲基化合物如丙二腈、氰基乙酸乙酯、氰基乙酰胺的缩合在室温下即能顺利进行，获得了很高的收率；而对于杂环芳醛、α，β-不饱和的醛以及脂肪醛与活泼亚甲基化合物的缩合，需在50~65℃下进行，也取得了很高的收率；对于脂肪酮、芳香酮以及二元醛与丙二腈的缩合在75~85℃下也能顺利地进行，获得中等以上的收率。

This work, concentrated on the asymmetric allylation of aldehydes controlled by different chiral auxiliaries prepared from rotational pure tartaric acid, can be divided into three parts.The first part aims to review the developments of chiral drugs and asymmetric synthesis, from which derived the present research topic backgrounds and works.Synthesis and applications of allylation from aldehydes are the second part of the thesis. By optimizing the reaction conditions, such as solvents, temperature, time and chiral auxiliaries like N,N\'-dibenzyl tartamide, N,N\'-p-dimethylphenyl tartamide, N,N\'-o-dimethylphenyl tartamide, N,N\'-o-dichlorophenyl tartamide, N,N\'-a-dinaphyl tartamide, N,N\'-dicyclohexyl tartamide and N,N\'-diphenyl tartamide, ideal experimenttal conditions are obtained according to HPLC monitoring, as well as the auxiliaries\' recoveries experiments. Starting from benzaldehyde and 3-bromopropaldehyde, N,N\'-dibenzyl tartamide is considered the best auxiliary in this reaction.

本文介绍了醛的不对称烯丙基化反应，以光学纯酒石酸为原料，研究了不同构型手性配体在醛的烯丙基化反应中的立体选择性，全文共分三部分十个章节：第一部分对当前手性药物和手性技术进行了概述，并由此展开了本文的研究背景和任务；第二部分为有机合成部分，对醛的不对称烯丙基化反应进行了深入探讨，以苯甲醛为原料对反应条件进行优化，在优化的反应条件下对制备的七种可回收手性酰胺配体(N-苄基酒石酸二酰胺、N-对甲苯基酒石酸二酰胺、N-邻甲苯基酒石酸二酰胺、N-邻氯苯基酒石酸二酰胺、N-a-萘基酒石酸二酰胺、N-环己基酒石酸二酰胺和N-苯基酒石酸二酰胺)进行筛选，优化配体回收实验条件，最终确定出N-苄基酒石酸二酰胺在苯甲醛的不对称烯丙基化反应中具有较大优越性，结晶回收的手性配体光学纯度保持不变。

Thirdly,in the view of some different results between the reaction of complexes(2)、(3)and[(Me_3Si)_2N]_3LnLi_3 with aromatic aldehydes, the reaction of 2 equiv of aromatic aldehydes with 1 equiv of lithium amide(1) catalyzed by the YCl_3 was subsequently studied,and better yields of the corresponding amides and alcohols can be isolated.These results indicated that the enolate ligand in complexes(2)、(3)may have impact on the Cannizzaro disproportionation reaction.

第三，鉴于上述配合物2、3和[(Me_3Si_2)2_N]_3LnLi_3与芳香醛反应结果上的一些差别，我们又以三氯化钇为催化剂，将两当量的芳香醛与一当量化合物1的锂盐直接进行反应，结果以较好的产率得到了相应的酰胺和醇，这说明配合物2、3中所含的乙烯醇基可能对此Cannizzaro-型歧化反应存在一定的影响。

For very long time, many research groups focus on using more than a stoichiometric amount of a chiral auxiliaries to obtain high enantioselectivity. There were mainly two sorts of processes reported on highly catalytic asymmetric addition of Grignard reagents to aldehydes. The former case was to transform Grignard reagent RMgX into other organometal reagents such as R_2Zn and R-Ti derivatives via complicated procedures at extremely low temperature. The later case was to link a chiral ligand to Mg in the form of organomagnesium amides or use chiral amine ligand catalyzing the alkylation of aldehydes.

格氏试剂对醛的不对称加成的报道大多需要大量的手性助剂以获得高的光学活性，而高度催化的格氏试剂对醛的不对称加成主要通过两种途径进行：一种是把格氏试剂转化成其他的有机金属试剂如R_2Zn和R-Ti化合物再对醛进行加成，反应通常在低温下进行；另一种是利用手性镁胺作为中间体或直接用手性胺催化来完成此反应。

Nevertheless, the yield of pinacol was also strongly affected by the steric environment surrounding the carbonyl group. The pinacol coupling of aromatic aldehydes has been achieved with high yields under such a condition. However, the diastereose-lectivities of pinacols were not satisfying. Unfortunately, the ketones and most aliphatic aldehydes appeared inert under the same reaction conditions.

然而， 呐偶合反应的产率受到羰基周围环境的立体位阻影响较大，在此条件下，锌粉能有效地促进芳香族醛类化合物进行水相呐偶合反应，得到的呐醇产率高，但非对映异构体选择性差，而脂肪族醛类化合物得到的呐醇产率较低，在同样的条件下，酮类化合物不能顺利进行呐偶合反应。

Carbohydrates are usually defined as polyhydroxy aldehydes and ketones or substances that hydrolyze to yield polyhydroxy aldehydes and ketones.

碳水化合物通常的定义是多羟基的醛和酮或者水解产生多羟基的醛和酮的物质。

In the negative and interrogative forms, of course, this is identical to the non-emphatic forms.

。但是，在否定句或疑问句里，这种带有"do"的方法表达的效果却没有什么强调的意思。

Go down on one's knees;kneel down

屈膝跪下。。。下跪祈祷