A poly-L β-hairpin bent stereochemically as a boat-shaped protein of mixed-L,D structure is scrutinized in basis of ordering as minimum of energy specific for its sequenceand solvent. The model suitable for the scrutiny is accomplished by design. A terminally-blocked oligoalanine is nucleated overDPro6-Gly7 and DPro6-LAsp7 dipeptide structures as a twelve-residue β-hairpin and bent stereochemically as a boat-shaped fold. The structure is inverse designed with side chains suitable to bind substrate p-nitophenyl phosphate, a surrogate substrate of acetyl choline and CO2. The designed sequences were proven by spectroscopy and molecular dynamics to order with solvent effects of water and display high binding affinity for the substrate. One of the proteins and a cognate oligoalanine are evolved with molecular dynamics to equilibrium in a solvent bath of water. Molecular dynamics studies establish that heteropolypeptide well ordered as β-hairpin fold and cognate oligoalanine as an ensemble of hairpin-like folds in water. The ordering of cognate oligoalanine as ensembles of hairpin-like folds manifests combined role of water as strong dielectric and weak dipolar solvent of peptides. The roles of stereochemistry and chemical details of sequence in defining polypeptides as energy minima under specific effect of solvent are illuminated and have been discussed.
{"title":"A Stereochemically-Bent β-Hairpin: Scrutiny of Folding by Comparing a Heteropolypeptide and Cognate Oligoalanine","authors":"K. R. Srivastava, S. Durani","doi":"10.4236/OJPC.2014.43012","DOIUrl":"https://doi.org/10.4236/OJPC.2014.43012","url":null,"abstract":"A poly-L β-hairpin bent stereochemically \u0000as a boat-shaped protein of mixed-L,D structure is scrutinized in basis of \u0000ordering as minimum of energy specific for its sequenceand solvent. The model \u0000suitable for the scrutiny is accomplished by design. A terminally-blocked \u0000oligoalanine is nucleated overDPro6-Gly7 and DPro6-LAsp7 dipeptide structures as a \u0000twelve-residue β-hairpin \u0000and bent stereochemically as a boat-shaped fold. The structure is inverse \u0000designed with side chains suitable to bind substrate p-nitophenyl phosphate, a \u0000surrogate substrate of acetyl choline and CO2. The designed \u0000sequences were proven by spectroscopy and molecular dynamics to order with \u0000solvent effects of water and display high binding affinity for the substrate. \u0000One of the proteins and a cognate oligoalanine are evolved with molecular \u0000dynamics to equilibrium in a solvent bath of water. Molecular dynamics studies \u0000establish that heteropolypeptide well ordered as β-hairpin fold and cognate \u0000oligoalanine as an ensemble of hairpin-like folds in water. The ordering of \u0000cognate oligoalanine as ensembles of hairpin-like folds manifests combined role \u0000of water as strong dielectric and weak dipolar solvent of peptides. The roles \u0000of stereochemistry and chemical details of sequence in defining polypeptides as \u0000energy minima under specific effect of solvent are illuminated and have been \u0000discussed.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
UV light photolysis of dichloroacetyl chloride (CHCl2COCl) has been investigated by infrared spectroscopy in cryogenic Ar, Kr, Xe, and O2 matrices. The formation of CHCl3 and CO was found to be the dominant process over the ketene formation. The C-C bond cleaved products CHCl2 and COCl were also observed. As the number of the chlorine atom substitution to methyl group of acetyl chloride increased, the C-C bond cleaved product yield in the triplet state increased, which can be attributed to an internal heavy-atom effect where the intersystem crossing rate was enhanced.
{"title":"Matrix Isolation and Computational Study on the Photolysis of CHCl2COCl","authors":"Nobuaki Tanaka","doi":"10.4236/OJPC.2014.43014","DOIUrl":"https://doi.org/10.4236/OJPC.2014.43014","url":null,"abstract":"UV light photolysis of \u0000dichloroacetyl chloride (CHCl2COCl) has been investigated by \u0000infrared spectroscopy in cryogenic Ar, Kr, Xe, and O2 matrices. The formation of CHCl3 and CO was found to be the dominant \u0000process over the ketene formation. The C-C bond cleaved products CHCl2 and COCl were also observed. As the \u0000number of the chlorine atom substitution to methyl group of acetyl chloride \u0000increased, the C-C bond cleaved product yield in the triplet state increased, \u0000which can be attributed to an internal heavy-atom effect where the intersystem \u0000crossing rate was enhanced.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The introduction of specific sites in organic frames for accommodation of various modes of bonding has been focused on reaction types which are described by using different theoretical models with or without a definite experimental proof. In this study three-center four-, three-, and two-electron systems based on carbon-, boron-, hydrogen-, and halogen exchange are under consideration. Based on the number of electrons in the transition state or transition complex it is shown that all transfer or exchange reactions share the same ratio numbers expressed as the quotient of the transitional bond distance under investigation and its normal bond length. With X-ray data of model systems it was even possible to give the ratio numbers for a three-center four-electron configuration experimental support with additional ab initio data. Furthermore a novel model type of substitution in organic chemistry is introduced through electrophilic insertion, informative for enzyme-substrate interactions based on the lock-and-key model. Reactions based on a three-center two-electron configuration mostly follow a nonlinear transition. In this alignment there will be a pursuit of cyclization for stabilization via homoaromaticity as homocyclopropenyl cation. The molecular dynamics of such a process is discussed based on recent X-ray crystallographic data of the symmetrically bridged, nonclassical geometry of the 2-norbornyl cation. In the present paper the focus is aimed at the transition intermediate of the (classical) 2-norbornyl cation involved in the isomerization into the nonclassical geometry. This model description is compared with a simple molecular rearrangement of the 1-propyl cation into the corner-protonated cyclopropane using the ab initio data. The exclusivity of the former isomerization compared with the latter one could be unambiguously demonstrated by the invention that theintramolecularelectron shift can be expressed in a linear relationship between the concerned electron-donating and accepting bond lengths. Finally, the fluor transitions as divalent atoms in a three-center two-electron configuration are described. The role of fluor in comparison with the other halogens is striking. The attention was focused on an excellent correspondence between the recent chemical and theoretical evidence for a symmetrical fluoronium ionin solution. Simple dialkylfluoroniumions in contrast to the other halonium ions are not present in solution. Although the geometry of the fluoronium ion theoretically can be described as a real minimum, the C-F-C angle of 120° is apparently the borderline transition for dissociation in C+ and F-C.
{"title":"Three-Center Configuration with Four,Three, and Two Electrons for Carbon,Boron, Hydrogen, and Halogen Exchange. A Model and Theoretical Study with Experimental Evidence","authors":"H. Buck","doi":"10.4236/OJPC.2014.42006","DOIUrl":"https://doi.org/10.4236/OJPC.2014.42006","url":null,"abstract":"The introduction of \u0000specific sites in organic frames for accommodation of various modes of bonding has \u0000been focused on reaction types which are described by using different \u0000theoretical models with or without a definite experimental proof. In this study \u0000three-center four-, three-, and two-electron systems based on carbon-, boron-, \u0000hydrogen-, and halogen exchange are under consideration. Based on the number of \u0000electrons in the transition state or transition complex it is shown that all \u0000transfer or exchange reactions share the same ratio numbers expressed as the \u0000quotient of the transitional bond distance under investigation and its normal \u0000bond length. With X-ray data of model systems it was even possible to give the \u0000ratio numbers for a three-center four-electron configuration experimental \u0000support with additional ab initio data. Furthermore a novel model type of substitution in organic chemistry is \u0000introduced through electrophilic insertion, informative for enzyme-substrate \u0000interactions based on the lock-and-key model. Reactions based on \u0000a three-center two-electron configuration mostly follow a nonlinear transition. \u0000In this alignment there will be a pursuit of cyclization for stabilization via \u0000homoaromaticity as homocyclopropenyl cation. The molecular dynamics of \u0000such a process is discussed based on recent X-ray \u0000crystallographic data of the symmetrically bridged, nonclassical geometry of \u0000the 2-norbornyl cation. In the present paper the focus is aimed at the \u0000transition intermediate of the (classical) 2-norbornyl cation involved in the \u0000isomerization into the nonclassical geometry. This model description is \u0000compared with a simple molecular rearrangement of the 1-propyl cation into the \u0000corner-protonated cyclopropane using the ab \u0000initio data. The exclusivity of the former isomerization compared with the \u0000latter one could be unambiguously demonstrated by the invention that theintramolecularelectron shift can be \u0000expressed in a linear relationship between the concerned electron-donating and \u0000accepting bond lengths. Finally, the fluor transitions as divalent atoms in a \u0000three-center two-electron configuration are described. The role of fluor in \u0000comparison with the other halogens is striking. The attention was focused on an \u0000excellent correspondence between the recent chemical and theoretical evidence \u0000for a symmetrical fluoronium ionin \u0000solution. Simple dialkylfluoroniumions in contrast to the other halonium \u0000ions are not present in solution. Although the geometry of the fluoronium ion theoretically \u0000can be described as a real minimum, the C-F-C angle of 120° is apparently the \u0000borderline transition for dissociation in C+ and F-C.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one of Lewis’s criteria. The same method was however rapidly applied to represent compounds that do not follow the octet-rule, i.e. compounds for which some of the composing atoms have greater or less than eight electrons in their valence shell. In a previous paper, an even-odd rule was proposed and shown to apply to both types of uncharged molecules. In the present paper, the even-odd rule is extended with the objective to encompass all single-bonded ions in one group: Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd representation is compatible with Lewis’s diagram. Additionally, each atom is subscripted with an even number calculated by adding the valence number, the number of covalent bonds of the element, and its electrical charge. This paper describes how to calculate the latter number and in doing so, how charge and electron-pairs can actually be precisely localized. Using ions known to be compatible with Lewis’s rule of eight, the even-odd rule is compared with the former. The even-odd rule is then applied to ions known as hypo- or hypervalent. An interesting side effect of the presented rule is that charge and electron-pairs are unambiguously assigned to one of the atoms composing the single-charged ion. Ions that follow the octet rule and ions that do not, are thus reconciled in one group called “electron-paired ions” due to the absence of unpaired electrons. A future paper will focus on the connection between the even-odd rule and molecules or ions having multiple bonds.
{"title":"Chemical Structural Formulas of Single-Bonded Ions Using the “Even-Odd” Rule Encompassing Lewis’s Octet Rule: Application to Position of Single-Charge and Electron-Pairs in Hypo- and Hyper-Valent Ions with Main Group Elements","authors":"G. Auvert","doi":"10.4236/OJPC.2014.42010","DOIUrl":"https://doi.org/10.4236/OJPC.2014.42010","url":null,"abstract":"Lewis developed a \u00002D-representation of molecules, charged or uncharged, known as structural \u0000formula, and stated the criteria to draw it. At the time, the vast majority of \u0000known molecules followed the octet-rule, one of Lewis’s criteria. The same \u0000method was however rapidly applied to represent compounds that do not follow \u0000the octet-rule, i.e. compounds for which some of the \u0000composing atoms have greater or less than eight electrons in their valence \u0000shell. In a previous paper, an even-odd rule was proposed and shown to apply to \u0000both types of uncharged molecules. In the present paper, the even-odd rule is \u0000extended with the objective to encompass all single-bonded ions in one group: \u0000Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd \u0000representation is compatible with Lewis’s diagram. Additionally, each atom is \u0000subscripted with an even number calculated by adding the valence number, the \u0000number of covalent bonds of the element, and its electrical charge. This paper \u0000describes how to calculate the latter number and in doing so, how charge and \u0000electron-pairs can actually be precisely localized. Using ions known to be \u0000compatible with Lewis’s rule of eight, the even-odd rule is compared with the \u0000former. The even-odd rule is then applied to ions known as hypo- or \u0000hypervalent. An interesting side effect of the presented rule is that charge \u0000and electron-pairs are unambiguously assigned to one of the atoms composing the \u0000single-charged ion. Ions that follow the octet rule and ions that do not, are \u0000thus reconciled in one group called “electron-paired ions” due to the absence \u0000of unpaired electrons. A future paper will focus on the connection between the \u0000even-odd rule and molecules or ions having multiple bonds.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In material science, half filled 3d orbital of transition metals is essentially an important factor controlling characteristics of alloys and compounds. This paper presents a result of the challenge of excitation of inner-core electron system with long lifetime of zinc films. The advanced zinc films with excited inner-core electron, 3dn (n = 9, 8). We report experimental results of XPS measurements of 9 points in the sample along vertical direction, respectively. The most pronounced futures are existence of satellites, which are about 4 eV higher than the main lines. According to the charge transfer mechanism proposed by A. Kotani and K. Okada, it was clarified that the origins of these peaks are c3d9L for the main peak and c3d9 for the satellite, respectively. From the energy difference, δEB, and peak intensity ratio, I+/I-, between c3d9 and c3d10L, the energy for charge transfer, Δ, and mixing energy, T, were estimated. In the region where the intensity of c3d10L becomes large, Δ becomes small, 1.2 Δdc = 5.5 eV and Udd = 5.5 eV. In the analysis along vertical direction, intensity profile of Zn3d9 showed odd functional symmetry and that of Zn3d10L showed even functional symmetry. Only the intensity profile of C1s (288 eV) showed the same spatial correlation with Zn3d9. In our experiment, the sample also showed high mobility of the constituting elements. These suggest that charge conservation in excited zinc atom suggests combination between Zn3d9 and C2-.
{"title":"Charge Transfer Mechanism and Spatial Density Correlation of Electronic States of Excited Zinc (3d 9 ) Films","authors":"Li Chen, M. Hamasaki, H. Manaka, K. Obara","doi":"10.4236/OJPC.2014.42007","DOIUrl":"https://doi.org/10.4236/OJPC.2014.42007","url":null,"abstract":"In material science, half filled 3d orbital of transition metals is essentially an important factor controlling characteristics of alloys and compounds. This paper presents a result of the challenge of excitation of inner-core electron system with long lifetime of zinc films. The advanced zinc films with excited inner-core electron, 3dn (n = 9, 8). We report experimental results of XPS measurements of 9 points in the sample along vertical direction, respectively. The most pronounced futures are existence of satellites, which are about 4 eV higher than the main lines. According to the charge transfer mechanism proposed by A. Kotani and K. Okada, it was clarified that the origins of these peaks are c3d9L for the main peak and c3d9 for the satellite, respectively. From the energy difference, δEB, and peak intensity ratio, I+/I-, between c3d9 and c3d10L, the energy for charge transfer, Δ, and mixing energy, T, were estimated. In the region where the intensity of c3d10L becomes large, Δ becomes small, 1.2 Δdc = 5.5 eV and Udd = 5.5 eV. In the analysis along vertical direction, intensity profile of Zn3d9 showed odd functional symmetry and that of Zn3d10L showed even functional symmetry. Only the intensity profile of C1s (288 eV) showed the same spatial correlation with Zn3d9. In our experiment, the sample also showed high mobility of the constituting elements. These suggest that charge conservation in excited zinc atom suggests combination between Zn3d9 and C2-.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Arab, M. I. Abdulsalam, Huda M. Alghamdi, K. Emran
316L SS alloy was tested under different applied potentials to study the susceptibility of this alloy to crevice corrosion. XPS measurements have been carried out to detect and define the products which formed on the surface of 316L SS in 3.5% NaCl at room temperature at applied potential = 200 mVSCE. The formation of Fe, Cr and Mo compounds were found, and these compounds play a great role in protecting the alloy which was found. The boundaries of the corroded area under washer teeth are in agreement with IR drop. The potentiodynamic technique is also studied to examine the overall corrosion behavior of 316L SS.
{"title":"The Crevice Corrosion of 316L SS Alloy in NaCl Solution at Different Applied Potentials","authors":"S. Arab, M. I. Abdulsalam, Huda M. Alghamdi, K. Emran","doi":"10.4236/OJPC.2014.42008","DOIUrl":"https://doi.org/10.4236/OJPC.2014.42008","url":null,"abstract":"316L SS alloy was tested under different \u0000applied potentials to study the susceptibility of this alloy to crevice \u0000corrosion. XPS measurements have been carried out \u0000to detect and define the products which formed on the surface of 316L SS in 3.5% NaCl at room temperature at \u0000applied potential = 200 mVSCE. \u0000The formation of Fe, Cr \u0000and Mo compounds were found, and these compounds play a great role in \u0000protecting the alloy which was found. The boundaries of the corroded area under \u0000washer teeth are in agreement with IR \u0000drop. The potentiodynamic technique is also studied to examine the overall \u0000corrosion behavior of 316L SS.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Roy, L. N. Roy, J. Dinga, Mathew R. Medcalf, Katherine E. Hundley, E. Hines, Clark B. Summers, Lucas S. Tebbe, Jamie Veliz
The acidic dissociation constant of N-(2-acetamido)-iminodiacetic acid monosodium (ADA) has been determined at 12 temperatures from 278.15 to 328.15 K by electromotive-force (emf) measurements of hydrogen-silver chloride cells without liquid junction. At 298.15 K, the value of the dissociation constant (pK2) is 6.8416 ± 0.0004. In response to the need for new physiological pH standards, buffer solutions of NaADA and its disodium salt, Na2ADA would be useful for pH control in the biological region of pH 6.5 to 7.5. The pK2 values over the experimental temperature range are given as a function of the thermodynamic temperature (T) by the equation pK2 = 2943.784/T - 47.05762 + 7.72703 ln T. At 298.15 K, standard thermodynamic quantities for the dissociation process have been derived from the temperature coefficients; ΔH° = 12,252 J·mol-1, ΔS° = -89.9 J·K-1·mol-1 and = -148 J·K-1·mol-1. The results are interpreted and compared with those of structurally related derivatives of GLYCINE.
{"title":"Dissociation Constant of N-(2-Acetamido)-Iminodiacetic Acid Monosodium (ADA) from (278.15 to 328.15) K","authors":"R. Roy, L. N. Roy, J. Dinga, Mathew R. Medcalf, Katherine E. Hundley, E. Hines, Clark B. Summers, Lucas S. Tebbe, Jamie Veliz","doi":"10.4236/OJPC.2014.42011","DOIUrl":"https://doi.org/10.4236/OJPC.2014.42011","url":null,"abstract":"The acidic dissociation \u0000constant of N-(2-acetamido)-iminodiacetic acid monosodium (ADA) has been \u0000determined at 12 temperatures from 278.15 to 328.15 K by electromotive-force \u0000(emf) measurements of hydrogen-silver chloride cells without liquid junction. \u0000At 298.15 K, the value of the dissociation constant (pK2) is 6.8416 \u0000± 0.0004. In response to the need for new physiological pH standards, buffer \u0000solutions of NaADA and its disodium salt, Na2ADA would be useful for \u0000pH control in the biological region of pH 6.5 to 7.5. The pK2 values over the experimental \u0000temperature range are given as a function of the thermodynamic temperature (T) \u0000by the equation pK2 = \u00002943.784/T - 47.05762 + 7.72703 ln T. At 298.15 K, standard thermodynamic \u0000quantities for the dissociation process have been derived from the temperature \u0000coefficients; ΔH° = 12,252 J·mol-1, ΔS° = -89.9 J·K-1·mol-1 and = \u0000-148 J·K-1·mol-1. The results are interpreted and \u0000compared with those of structurally related derivatives of GLYCINE.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As Lewis proposed his octet rule, itself inspired by Abegg’s rule, that a molecule is stable when all its composing atoms have eight electrons in their valence shell, it perfectly applied to the vast majority of known stable molecules. Only a few stable molecules were known that didn’t fall under this rule, such as PCl5 and SF6, and Lewis chose to leave them aside at the time of his research. With further advances in chemistry, more exceptions to this rule of eight have been found, usually with the central atom of the structure having more or less than eight electrons in its valence shell. Theories have been developed in order to modify the octet rule to suit these molecules, defining these as hyper- or hypo-valent molecules and using other configurations for the electrons. The present paper aims to propose a representation rule for gaseous single-bonded molecules that makes it possible to reconcile both; molecules following the octet theory and those which do not. In this representation rule, each element of the molecule is subscripted with two numbers that follow a set of simple criteria. The first represents the number of valence electrons of the element; while the second is calculated by adding the first number to the number of the element’s covalent bonds within the molecule. The latter is equal to eight for organic molecules following the octet rule. Molecules being exceptions to the octet rule are now encompassed by this new even-odd rule: they have a valid chemical structural formula in which the second number is even but not always equal to eight. Both rules—octet and even-odd—are discussed and compared, using several well-known gaseous molecules having one or several single-bonded elements. A future paper will discuss the application of the even-odd rule to charged molecules.
{"title":"Improvement of the Lewis-Abegg-Octet Rule Using an “Even-Odd” Rule in Chemical Structural Formulas: Application to Hypo and Hyper-Valences of Stable Uncharged Gaseous Single-Bonded Molecules with Main Group Elements","authors":"G. Auvert","doi":"10.4236/OJPC.2014.42009","DOIUrl":"https://doi.org/10.4236/OJPC.2014.42009","url":null,"abstract":"As Lewis proposed his octet rule, itself inspired by Abegg’s rule, that a molecule is stable when all its composing atoms have eight electrons in their valence shell, it perfectly applied to the vast majority of known stable molecules. Only a few stable molecules were known that didn’t fall under this rule, such as PCl5 and SF6, and Lewis chose to leave them aside at the time of his research. With further advances in chemistry, more exceptions to this rule of eight have been found, usually with the central atom of the structure having more or less than eight electrons in its valence shell. Theories have been developed in order to modify the octet rule to suit these molecules, defining these as hyper- or hypo-valent molecules and using other configurations for the electrons. The present paper aims to propose a representation rule for gaseous single-bonded molecules that makes it possible to reconcile both; molecules following the octet theory and those which do not. In this representation rule, each element of the molecule is subscripted with two numbers that follow a set of simple criteria. The first represents the number of valence electrons of the element; while the second is calculated by adding the first number to the number of the element’s covalent bonds within the molecule. The latter is equal to eight for organic molecules following the octet rule. Molecules being exceptions to the octet rule are now encompassed by this new even-odd rule: they have a valid chemical structural formula in which the second number is even but not always equal to eight. Both rules—octet and even-odd—are discussed and compared, using several well-known gaseous molecules having one or several single-bonded elements. A future paper will discuss the application of the even-odd rule to charged molecules.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Egharevba Felix, Ogbebor Clara, Akpoveta Oshevwiyo Vincent
The rate of cane sugar fermentation with Saccharomyces cerevisiae was studied at temperatures between 30°C and 42°C in order to characterize the process using thermodynamic parameters such as enthalpy (ΔH*), activation energy (ΔE*), entropy (ΔS*), Gibbs free energy (ΔG*) and equilibrium constant (K). The parameters were evaluated on the basis of a consideration of Arrhenius, Eyring and Van’t Hoff’s equations. The results obtained are ΔH*, 91.85 KJ·mol-1; ΔE*, 91.85 KJ·mol-1, ΔS*, 2763 J·mol-1K-1; ΔG*, -762.09 KJ·mol-1, and equilibrium constant, K, 1.34 dm3·mol-1. These values were subsequently used to obtain by calculation the rate constant of the fermentation k, 1.43 × 1011 min-1, Arrhenius constant A (pre-exponential or frequency factor), 4.79 × 1026 min-1, orientation parameter, P, 4.48 × 1015 and the collision frequency Z, 1.07 × 1011 min-1. Finally the fermentation efficiency calculated on the basis of a complete combustion of glucose is 377.8%. The results showed that though the fermentation process is kinetically controlled, it is suggested that the positive impact of the feasible thermodynamics is limited by other process variables.
{"title":"Thermodynamic Characterization of Saccharomyces cerevisiae Catalyzed Fermentation of Cane Sugar","authors":"Egharevba Felix, Ogbebor Clara, Akpoveta Oshevwiyo Vincent","doi":"10.4236/OJPC.2014.41004","DOIUrl":"https://doi.org/10.4236/OJPC.2014.41004","url":null,"abstract":"The rate of cane sugar fermentation with Saccharomyces cerevisiae was studied at temperatures between 30°C and 42°C in order to characterize the process using thermodynamic parameters such as enthalpy (ΔH*), activation energy (ΔE*), entropy (ΔS*), Gibbs free energy (ΔG*) and equilibrium constant (K). The parameters were evaluated on the basis of a consideration of Arrhenius, Eyring and Van’t Hoff’s equations. The results obtained are ΔH*, 91.85 KJ·mol-1; ΔE*, 91.85 KJ·mol-1, ΔS*, 2763 J·mol-1K-1; ΔG*, -762.09 KJ·mol-1, and equilibrium constant, K, 1.34 dm3·mol-1. These values were subsequently used to obtain by calculation the rate constant of the fermentation k, 1.43 × 1011 min-1, Arrhenius constant A (pre-exponential or frequency factor), 4.79 × 1026 min-1, orientation parameter, P, 4.48 × 1015 and the collision frequency Z, 1.07 × 1011 min-1. Finally the fermentation efficiency calculated on the basis of a complete combustion of glucose is 377.8%. The results showed that though the fermentation process is kinetically controlled, it is suggested that the positive impact of the feasible thermodynamics is limited by other process variables.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. H. Ansari, Anand Trivedi, D. Sharma, P. Chandra
Refractive indices of the six binary mixtures between N-Butyl bromide with Aniline, Benzene, Xylene, Carbon tetrachloride, n-Heptane and Toluene for the entire concentration range have been measured at 303.15 K. Furthermore, deviation in refractive indices from ideal mixture, molar refraction, deviation in molar refraction from ideal values for these mixtures has also been evaluated. The results are discussed in term of molecular interactions between the components of the binary mixtures.
{"title":"Refractometric Studies on Molecular Interactions in Six Binary Liquid Mixtures","authors":"N. H. Ansari, Anand Trivedi, D. Sharma, P. Chandra","doi":"10.4236/OJPC.2014.41001","DOIUrl":"https://doi.org/10.4236/OJPC.2014.41001","url":null,"abstract":"Refractive \u0000indices of the six binary mixtures between N-Butyl bromide with Aniline, \u0000Benzene, Xylene, Carbon tetrachloride, n-Heptane and Toluene for the entire \u0000concentration range have been measured at 303.15 K. Furthermore, deviation in refractive indices from ideal mixture, \u0000molar refraction, deviation in molar refraction from ideal values for these \u0000mixtures has also been evaluated. The results are discussed in term of \u0000molecular interactions between the components of the binary mixtures.","PeriodicalId":59839,"journal":{"name":"物理化学期刊(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70501598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：