A SYSTEM OF MOLECULAR THERMOCHEMISTRY FOR ORGANIC GASES AND LIQUIDS

1956 ◽  
Vol 34 (5) ◽  
pp. 626-648 ◽  
Author(s):  
Keith J. Laidler
Keyword(s):  
Hydrogen Bonds ◽  
Heats Of Formation ◽  
Multiple Bonds ◽  
Aromatic Molecules ◽  
Tertiary Carbon ◽  
Systematic Effects ◽  
Heats Of Combustion ◽  
Organic Gases ◽  
Heats Of Vaporization ◽  
Good Agreement

An analysis has been made of the heats of formation and combustion of organic gases and liquids, and of the heats of vaporization of liquids. The work has been done as far as possible with homologous series, in order to discover systematic effects. The data are converted into heats of atomization, i.e., the heats required to convert the gases or liquids into their constituent atoms. It is shown that the heats of atomization of the gaseous aliphatic hydrocarbons (paraffins, olefins, and acetylenes) can be accurately represented by a scheme in which a distinction is made between primary, secondary, and tertiary carbon–hydrogen bonds, and between bonds that are next to, and next but one to, multiple bonds. For aromatic molecules an appropriate correction for resonance is proposed. For other types of compound it is found that suitable values for the various bonds (e.g., C–CHO, C–OH) will give rise to good agreement with experiment.It is shown that to a reliable approximation heats of vaporization are also amenable to the same treatment. Since this is so it is possible to assign bond values on the basis of which it is possible to make predictions about heats of formation of liquids.A system of coefficients is worked out by means of which the numbers of atoms of various kinds in a molecule can be expressed in terms of the numbers of the different kinds of bonds. On the basis of these it is shown how bond contributions to heats of formation and heats of combustion can be calculated. A table (Table X) gives the contributions proposed for the heats of atomization, heats of formation, and heats of combustion for both gases and liquids.

scholarly journals Curcumin Inhibits the Primary Nucleation of Amyloid-Beta Peptide: A Molecular Dynamics Study

Biomolecules ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1323
Author(s):  
Irini Doytchinova ◽  
Mariyana Atanasova ◽  
Evdokiya Salamanova ◽  
Stefan Ivanov ◽  
Ivan Dimitrov
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonds ◽  
Amyloid Beta ◽  
Amyloid Plaques ◽  
Amyloid Beta Peptide ◽  
Aβ Peptides ◽  
Amyloid Peptides ◽  
Primary Nucleation ◽  
Beta Peptide ◽  
Good Agreement

The amyloid plaques are a key hallmark of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. Amyloidogenesis is a complex long-lasting multiphase process starting with the formation of nuclei of amyloid peptides: a process assigned as a primary nucleation. Curcumin (CU) is a well-known inhibitor of the aggregation of amyloid-beta (Aβ) peptides. Even more, CU is able to disintegrate preformed Aβ firbils and amyloid plaques. Here, we simulate by molecular dynamics the primary nucleation process of 12 Aβ peptides and investigate the effects of CU on the process. We found that CU molecules intercalate among the Aβ chains and bind tightly to them by hydrogen bonds, hydrophobic, π–π, and cation–π interactions. In the presence of CU, the Aβ peptides form a primary nucleus of a bigger size. The peptide chains in the nucleus become less flexible and more disordered, and the number of non-native contacts and hydrogen bonds between them decreases. For comparison, the effects of the weaker Aβ inhibitor ferulic acid (FA) on the primary nucleation are also examined. Our study is in good agreement with the observation that taken regularly, CU is able to prevent or at least delay the onset of neurodegenerative disorders.

Computational Determination of Heats of Formation of Energetic Compounds

1995 ◽  
Vol 418 ◽  
Author(s):  
Peter Politzer ◽  
Jane S. Murray ◽  
M. Edward Grice
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Functional Group ◽  
Solid Phase ◽  
Heats Of Formation ◽  
Energetic Compounds ◽  
Phase Data ◽  
Heats Of Vaporization ◽  
Group Effects

AbstractA recently-developed density functional procedure for computing gas phase heats of formation is briefly described and results for several categories of energetic compounds are summarized and discussed. Liquid and solid phase values can be obtained by combining the gas phase data with heats of vaporization and sublimation estimated by means of other relationships. Some observed functional group effects upon heats of formation are noted.

Heats of vaporization and gaseous heats of formation of some five- and six-membered ring alkenes

1979 ◽  
Vol 57 (17) ◽  
pp. 2302-2304 ◽  
Author(s):  
Richard Fuchs ◽  
L. Alan Peacock
Keyword(s):  
Gas Chromatography ◽  
Double Bond ◽  
Heat Capacities ◽  
Membered Ring ◽  
Heats Of Formation ◽  
Group Additivity ◽  
Liquid Heat ◽  
Heats Of Vaporization

The heats of vaporization of 1-methylcyclopentene, 3-methylcyclopentene, ethylidenecyclopentane, 1-ethylcyclopentene, methylenecyclohexane, allylcyclopentane, vinylcyclohexane, ethylidenecyclohexane, allylcyclohexane, 3,3-diethylpentane, 2,2,4,4-tetramethylpentane, and trans-2,2,5,5-tetramethyl-3-hexene have been measured by the gas chromatography – calorimetry method. These values have been combined with previously reported liquid heats of formation to give gaseous values of ΔHf. The results indicate that the internal double bond is favored by about 0.5 kcal over the exo in both 5- and 6-membered rings, but the endo–exo differences are much smaller than previously believed. Several of the liquid heat capacities that were measured were not well predicted by group additivity schemes.

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