scholarly journals Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part II

AppliedChem ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 111-129
Author(s):  
Robert J. Meier
Keyword(s):  
Process Design ◽  
Organic Molecules ◽  
Contemporary Literature ◽  
Heat Of Formation ◽  
Group Contribution ◽  
Thermochemical Properties ◽  
High Quality ◽  
Flexible Part ◽  
Torsional Angles ◽  
The Enthalpy Of Formation

Group contribution (GC) methods to predict thermochemical properties are eminently important to process design. We present a group contribution parametrization for the heat of formation of organic molecules exhibiting chemical accuracy, maximum 1 kcal/mol (4.2 kJ/mol) difference between experiment and model values while minimizing the number of parameters avoiding overfitting and therewith avoiding reduced predictability. Compared to the contemporary literature, this was successfully achieved by employing available literature high-quality and consistent experimental data, optimizing parameters group by group, and introducing additional parameters when chemical understanding was obtained supporting these. A further important result is the observation that the applicability of the group contribution approach breaks down with increasing substitution levels, i.e., more heavily alkyl-substituted molecules, the reason being a serious influence of substitution on the conformation of the flexible part of the entire molecule within particular valence angles and torsional angles affected, which cannot be accounted for by additional GC parameters with fixed numerical values.

scholarly journals Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy”

2021 ◽  
Vol 5 (2) ◽  
pp. 24
Author(s):  
Robert J. Meier
Keyword(s):  
Process Design ◽  
Organic Molecules ◽  
Optimal Parameter ◽  
Heat Of Formation ◽  
Group Contribution ◽  
Data Set ◽  
Additional Group ◽  
Chemical Knowledge ◽  
Parameter Values ◽  
The Enthalpy Of Formation

Group contribution (GC) methods to predict thermochemical properties are of eminent importance to process design. Compared to previous works, we present an improved group contribution parametrization for the heat of formation of organic molecules exhibiting chemical accuracy, i.e., a maximum 1 kcal/mol (4.2 kJ/mol) difference between the experiment and model, while, at the same time, minimizing the number of parameters. The latter is extremely important as too many parameters lead to overfitting and, therewith, to more or less serious incorrect predictions for molecules that were not within the data set used for parametrization. Moreover, it was found to be important to explicitly account for common chemical knowledge, e.g., geminal effects or ring strain. The group-related parameters were determined step-wise: first, alkanes only, and then only one additional group in the next class of molecules. This ensures unique and optimal parameter values for each chemical group. All data will be made available, enabling other researchers to extend the set to other classes of molecules.

scholarly journals Simple and efficient modifications of well known techniques for reliable growth of high-quality crystals of small bioorganic molecules

2014 ◽  
Vol 47 (4) ◽  
pp. 1435-1442 ◽  
Author(s):  
Denis A. Rychkov ◽  
Sergey G. Arkhipov ◽  
Elena V. Boldyreva
Keyword(s):  
Amino Acids ◽  
Secondary School ◽  
Organic Molecules ◽  
Poor Quality ◽  
Chemical Degradation ◽  
School Level ◽  
Chemistry Curriculum ◽  
High Quality ◽  
Small Organic Molecules ◽  
Secondary School Level

A number of modifications to traditional techniques are suggested in order to overcome problems that frequently arise when growing crystals from solution. These improvements, and their combination, help to avoid problems such as poor nucleation, the spontaneous precipitation of many poor-quality small powder-like crystals, crystals adhering to the crystallization vessel or to each other, and chemical degradation of the solution. The proposed techniques can be used to crystallize desirable metastable polymorphs reliably. None of the suggested methods demands the usage of any special or expensive equipment, or specific skills, and they can be implemented in the chemistry curriculum even at secondary school level. Examples are given for the crystallization of small organic molecules such as carboxylic acids, amino acids, pharmaceuticals etc., but the same techniques are applicable to other classes of compound.

Advanced technology of process design for high-quality bar and wire-rod production

1982 ◽  
Vol 9 (1) ◽  
pp. 46-51
Author(s):  
S. Kojima ◽  
T. Ohnishi ◽  
T. Saito ◽  
K. Oka
Keyword(s):  
Process Design ◽  
Advanced Technology ◽  
High Quality ◽  
Wire Rod

Process Design on Baogang 2250mm Hot Rolling Project

2013 ◽  
Vol 744 ◽  
pp. 283-287
Author(s):  
Lin Li ◽  
Fu Ming Zhang ◽  
Hong Wen Liu ◽  
Ruo Yu Zang ◽  
Fan Wang
Keyword(s):  
Hot Rolling ◽  
Process Design ◽  
Raw Materials ◽  
International Standards ◽  
Design Flow ◽  
Utilization Efficiency ◽  
High Quality ◽  
Flow Process ◽  
Production Scale ◽  
Starting Point

Based on scale and output, process design assures high-end products for Baogang, ensures advancement and reliability of devices, enhances Chinese split supply ratio; ability to decrease investment and implement sustainable scientific outlook on development. To introduce production scale and product scheme in Baogang 2250mm hot rolling project, and illustrate design flow, process arrangement and equipment level. Ability to insist on a high starting point, reference to international standards, use advanced devices in order to meet high-quality needs and achieve strong competitiveness, adhere to strategy of sustainable development, improve on utilization efficiency of raw materials, energy and water, accomplish cyclic utilization. Leading products are high-quality rare-earth auto plates, steel sheets for home electrical appliances. The layout of plant is tightly linked with process design and whole plan, short process, smooth logistics, less middle stages and advanced automatic control system create international level in 21st century.

scholarly journals Barrier to Rotation about Sulfur-Sulfur Bonds in Homocyclic Sulfur Molecules

1983 ◽  
Vol 38 (5) ◽  
pp. 543-545 ◽  
Author(s):  
Ralf Steudel
Keyword(s):  
Enthalpy Of Formation ◽  
Bond Distance ◽  
Torsional Angles ◽  
The Enthalpy Of Formation

AbstractIt is shown that the distances (d) of the 19 longest bonds in 9 homocyclic sulfur rings of type Sn (n = 6-20) depend on the torsional angles (τ) which vary between 0° and 140°. The function d = f(τ) is smallest for τ = 90-100° and largest for τ = 0°; the corresponding bond distance variation amounts to 13 pm or 6%. The height of the torsional cis-barrier is estimated from the enthalpy of formation of gaseous S7 as equal to or smaller than 24 kJ/mol.

Preparation of high quality Microgranulate CrO3 based on green process design

2017 ◽  
Vol 95 (7) ◽  
pp. 1261-1268
Author(s):  
Wenwen Cui ◽  
Ping Li ◽  
Yongan Chen ◽  
Chuang Liu ◽  
Hailin Zhang ◽  
...  
Keyword(s):  
Process Design ◽  
Green Process ◽  
High Quality
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