Nucleophilicity and its parametrization

1989 ◽  
Vol 54 (1) ◽  
pp. 117-135
Author(s):  
Oldřich Pytela ◽  
Vítězslav Zima

The method of conjugate deviations based on the regression analysis has been suggested for construction of a new nucleophilicity scale. This method has been applied to a set of 28 nucleophiles participating in 47 physical and chemical processes described in literature. The two-parameter nucleophilicity scale obtained represents-in the parameter denoted as ND-the general tendency to form a bond to an electrophile predominantly on the basis of the orbital interaction and-in the parameter denoted as PD-the ability to interact with a centre similar to the proton (basicity). The linear correlation equation involving the ND, PD parameters and the charge appears to be distinctly better than the most significant relations used. The correlation dependences have the physico-chemical meaning. From the position of individual nucleophiles in the space of the ND and PD parameters, some general conclusions have been derived about the factors governing the reactivity of nucleophiles.

2021 ◽  
pp. 19-23
Author(s):  
Елена Васильевна Дубинина ◽  
Людмила Николаевна Крикунова ◽  
Владимир Александрович Трофимченко ◽  
Кантемир Витальевич Небежев

На качество фруктовых дистиллятов оказывают существенное влияние различные физико-химические процессы, проходящие в дистилляционной установке под действием высокой температуры. В зависимости от особенностей биохимического состава для каждого вида сырья необходимо подбирать конкретные режимы дистилляции, обеспечивающие получение дистиллята с высокими органолептическими и физико-химическими характеристиками. В связи с этим цель работы состояла в исследовании влияния режимных параметров фракционированной дистилляции сброженной кизиловой мезги на распределение летучих компонентов по фракциям. В качестве объектов исследования в работе использовали фракции, полученные в процессе дистилляции сброженной кизиловой мезги на установке прямой сгонки «Kothe Distillationstechnik» (Германия). Экспериментально установлено, что повышение скорости при дистилляции сброженной кизиловой мезги приводит к увеличению объема отбираемой головной фракции, при одновременном снижении ее крепости. Показано, что изменение скорости дистилляции приводит к изменению характера перехода основных летучих компонентов в дистиллят и распределения их по фракциям. Изучена динамика перехода летучих компонентов в дистиллят при различных режимах работы дистилляционной установки - без задержки флегмы (обычный режим) и с задержкой флегмы на нижней тарелке укрепляющей колонны. Проведенные исследования показали, что при условии медленной дистилляции со скоростью не более 5,5 см3/мин в средние фракции переходит 82-85% компонентов энантового эфира, а содержание ацетальдегида снижается на 10-12% по сравнению с быстрой дистилляцией. Показано, что применение задержки флегмы на нижней тарелке укрепляющей колонны дистилляционной установки также способствует снижению перехода в кизиловый дистиллят ацетальдегида и этилацетата, и к сокращению потерь компонентов энантового эфира с головной и хвостовой фракциями. The quality of fruit distillates is significantly affected by various physical and chemical processes that take place in the distillation unit under the influence of high temperature. Depending on the characteristics of the biochemical composition for each type of raw material, it is necessary to select specific distillation modes that ensure the production of distillate with high organoleptic and physico-chemical characteristics. In this regard, the aim of the work was to study the influence of the regime parameters of fractionated distillation of fermented Cornel pulp on the distribution of volatile components by fractions. The fractions obtained during the distillation of fermented Cornel pulp at the direct distillation unit «Kothe Distillationstechnik» (Germany), were used as the objects of research. It is experimentally established that an increase in the speed during distillation of fermented Cornel pulp leads to an increase in the volume of the selected head fraction, while reducing its strength. It is shown that a change in the distillation rate leads to a change in the nature of the transition of the main volatile components to the distillate and their distribution by fractions. The dynamics of the transition of volatile components to distillate under different operating modes of the distillation unit - without phlegm delay (normal mode) and with phlegm delay on the lower plate of the reinforcing column is studied. Studies have shown that under the condition of slow distillation at a speed of no more than 5.5 cm3/min, 82-85% of the enantium ether components pass into the medium fractions, and the content of acetaldehyde decreases by 10-12% compared to fast distillation. It is shown that the use of phlegm delay on the lower plate of the strengthening column of the distillation unit also helps to reduce the transition to the Cornel distillate of acetaldehyde and ethyl acetate, and to reduce the loss of the components of the enantium ether with the head and tail fractions.


2001 ◽  
Vol 32 (3) ◽  
pp. 133-141 ◽  
Author(s):  
Gerrit Antonides ◽  
Sophia R. Wunderink

Summary: Different shapes of individual subjective discount functions were compared using real measures of willingness to accept future monetary outcomes in an experiment. The two-parameter hyperbolic discount function described the data better than three alternative one-parameter discount functions. However, the hyperbolic discount functions did not explain the common difference effect better than the classical discount function. Discount functions were also estimated from survey data of Dutch households who reported their willingness to postpone positive and negative amounts. Future positive amounts were discounted more than future negative amounts and smaller amounts were discounted more than larger amounts. Furthermore, younger people discounted more than older people. Finally, discount functions were used in explaining consumers' willingness to pay for an energy-saving durable good. In this case, the two-parameter discount model could not be estimated and the one-parameter models did not differ significantly in explaining the data.


Food Industry ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 16-22
Author(s):  
Irina Reznichenko ◽  
Maria Kondratieva

The article concerns the counterfeiting problem of non-alcoholic drinks sold on the consumer market of the Russian Federation; provides data on drinks fraud methods (assortment, qualitative, quantitative and informational types). Strengthening quality control of soft drinks is one of the main directions of providing consumers with qualitative products. The authors presented authenticity identification results of carbonated soft drinks sold on the Kemerovo consumer market for compliance with the current regulatory documents requirements; run the consumer criteria analysis for the drinks identification of various brands. They obtained data on the labeling and packaging identification of selected non-alcoholic carbonated drinks samples for the compliance with current regulatory documents. A man recorded the compliance. There was an absence of the quantitative counterfeiting identification. The study described results of the organoleptic and physico-chemical quality indicators research. According to the GOST 28188-2014 “Non-Alcoholic Beverages. General Technical Conditions” the authors evaluated beverages quality by such physical and chemical indicators as the mass fraction of dry substances, acidity, and the mass fraction of carbon dioxide. The researchers run the organoleptic indicators analysis according to a score system. Authenticity identification of the selected drinks samples showed that there are no signs of counterfeiting and the products are of high quality.


Author(s):  
Andrew Steane

The life of an ordinary tree is described, in terms of the main physical and chemical processes: carbon capture by photosynthesis; entropy and energy; moisture. The information expressed in the tree comes partly from the DNA and partly from the sunlight. The tree does not push upwards from the ground, but solidifies the air.


ACS Photonics ◽  
2019 ◽  
Vol 6 (12) ◽  
pp. 3039-3056 ◽  
Author(s):  
Vanessa N. Peters ◽  
Srujana Prayakarao ◽  
Samantha R. Koutsares ◽  
Carl E. Bonner ◽  
Mikhail A. Noginov

2021 ◽  
Vol 8 (3) ◽  
pp. 030401
Author(s):  
Roger Narayan ◽  
James Yoo ◽  
Anthony Atala

2008 ◽  
Vol 54 (1) ◽  
pp. 116-122 ◽  
Author(s):  
Samuel Caillou ◽  
Patrick A. Gerin ◽  
Cristèle J. Nonckreman ◽  
Sandrine Fleith ◽  
Christine C. Dupont-Gillain ◽  
...  

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