Energetic Molecules As Future Octane Boosters: Theoretical And
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The Conformations of Cycloalkanes
The Conformations of Cycloalkanes Ring-containing structures are a common occurrence in organic chemistry. We must, therefore spend some time studying the special characteristics of the parent cycloalkanes. Cyclical connectivity imposes constraints on the range of motion that the atoms in rings can undergo. Cyclic molecules are thus more rigid than linear or branched alkanes because cyclic structures have fewer internal degrees of freedom (that is, the motion of one atom greatly influences the motion of the others when they are connected in a ring). In this lesson we will examine structures of the common ring structures found in organic chemistry. The first four cycloalkanes are shown below. cyclopropane cyclobutane cyclopentane cyclohexane The amount of energy stored in a strained ring is estimated by comparing the experimental heat of formation to the calculated heat of formation. The calculated heat of formation is based on the notion that, in the absence of strain, each –CH2– group contributes equally to the heat of formation, in line with the behavior found for the acyclic alkanes (i.e., open chains). Thus, the calculated heat of formation varies linearly with the number of carbon atoms in the ring. Except for the 6-membered ring, the experimental values are found to have a more positive heat of formation than the calculated value owning to ring strain. The plots of calculated and experimental enthalpies of formation and their difference (i.e., ring strain) are seen in the Figure. The 3-membered ring has about 27 kcal/mol of strain. It can be seen that the 6-membered ring possesses almost no ring strain. -
First Principles Prediction of Thermodynamic Properties
2 First Principles Prediction of Thermodynamic Properties Hélio F. Dos Santos and Wagner B. De Almeida NEQC: Núcleo de Estudos em Química Computacional, Departamento de Química, ICE Universidade Federal de Juiz de Fora (UFJF), Campus Universitário Martelos, Juiz de Fora LQC-MM: Laboratório de Química Computacional e Modelagem Molecular Departamento de Química, ICEx, Universidade Federal de Minas Gerais (UFMG) Campus Universitário, Pampulha, Belo Horizonte Brazil 1. Introduction The determination of the molecular structure is undoubtedly an important issue in chemistry. The knowledge of the tridimensional structure allows the understanding and prediction of the chemical-physics properties and the potential applications of the resulting material. Nevertheless, even for a pure substance, the structure and measured properties reflect the behavior of many distinct geometries (conformers) averaged by the Boltzmann distribution. In general, for flexible molecules, several conformers can be found and the analysis of the physical and chemical properties of these isomers is known as conformational analysis (Eliel, 1965). In most of the cases, the conformational processes are associated with small rotational barriers around single bonds, and this fact often leads to mixtures, in which many conformations may exist in equilibrium (Franklin & Feltkamp, 1965). Therefore, the determination of temperature-dependent conformational population is very much welcomed in conformational analysis studies carried out by both experimentalists and theoreticians. -
Comparing Models for Measuring Ring Strain of Common Cycloalkanes
The Corinthian Volume 6 Article 4 2004 Comparing Models for Measuring Ring Strain of Common Cycloalkanes Brad A. Hobbs Georgia College Follow this and additional works at: https://kb.gcsu.edu/thecorinthian Part of the Chemistry Commons Recommended Citation Hobbs, Brad A. (2004) "Comparing Models for Measuring Ring Strain of Common Cycloalkanes," The Corinthian: Vol. 6 , Article 4. Available at: https://kb.gcsu.edu/thecorinthian/vol6/iss1/4 This Article is brought to you for free and open access by the Undergraduate Research at Knowledge Box. It has been accepted for inclusion in The Corinthian by an authorized editor of Knowledge Box. Campring Models for Measuring Ring Strain of Common Cycloalkanes Comparing Models for Measuring R..ing Strain of Common Cycloalkanes Brad A. Hobbs Dr. Kenneth C. McGill Chemistry Major Faculty Sponsor Introduction The number of carbon atoms bonded in the ring of a cycloalkane has a large effect on its energy. A molecule's energy has a vast impact on its stability. Determining the most stable form of a molecule is a usefol technique in the world of chemistry. One of the major factors that influ ence the energy (stability) of cycloalkanes is the molecule's ring strain. Ring strain is normally viewed as being directly proportional to the insta bility of a molecule. It is defined as a type of potential energy within the cyclic molecule, and is determined by the level of "strain" between the bonds of cycloalkanes. For example, propane has tl1e highest ring strain of all cycloalkanes. Each of propane's carbon atoms is sp3-hybridized. -
Text Related to Segment 5.02 ©2002 Claude E. Wintner from the Previous Segment We Have the Value of the Heat of Combustion Of
Text Related to Segment 5.02 ©2002 Claude E. Wintner From the previous segment we have the value of the heat of combustion of an "unstrained" methylene unit as -157.4 kcal/mole. On this basis one would predict that combustion of "unstrained" cyclopropane should liberate 3 X 157.4 = 472.2 kcal/mole; however, when cyclopropane is burned, a value of 499.8 kcal/mole is measured for the actual heat of combustion. The difference of 27.6 kcal/mole is interpreted as representing the higher internal energy ("strain energy") of real cyclopropane as compared to a postulated strain-free "model." ("Model" in this usage speaks of a proposal, or postulate.) These facts are graphed conveniently on an energy diagram as follows: "Strain Energy" represents the error units: kcal/mole not to scale in the "strain-free model" real cyclopropane + 4.5 O2 27.6 "strain-free model" of cyclopropane 499.8 observed heat of combustion + 4.5 O2 472.2 3CO2 + 3H2O heat of combustion predicted for "strain-free model" Note that this estimate of the strain energy in cyclopropane amounts to 9.2 kcal/mole of strain per methylene group (dividing 27.6 by 3, because of the three carbon atoms). Comparable values in kcal/mole for other small and medium rings are given in the following table. As one might expect, in general the strain decreases as the ring is enlarged. units: kcal/mole n Total Strain Strain per CH2 3 27.6 9.2 (CH2)n 4 26.3 6.6 5 6.2 1.2 6 0.1 0.0 ! 7 6.2 0.9 8 9.7 1.2 9 12.6 1.4 10 12.4 1.2 12 4.1 0.3 15 1.9 0.1 Without entering into a discussion of the relevant bonding concepts here, and instead relying on geometry alone, interpretation of the source of the strain energy in cyclopropane and cyclobutane is to some extent self-evident. -
The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy”
chemengineering Article Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Robert J. Meier Pro-Deo Consultant, 52525 Heinsberg, North-Rhine Westphalia, Germany; [email protected] Abstract: Group contribution (GC) methods to predict thermochemical properties are of eminent importance to process design. Compared to previous works, we present an improved group contri- bution 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. Keywords: enthalpy of formation; thermodynamics; molecular modeling; group contribution method; quantum mechanical method; chemical accuracy; process design Citation: Meier, R.J. Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy”. 1. Introduction ChemEngineering 2021, 5, 24. To understand chemical reactivity and/or chemical equilibria, knowledge of thermo- o https://doi.org/10.3390/ dynamic properties such as gas-phase standard enthalpy of formation DfH gas is a necessity. -
Baeyer Strain Theory Introduction Van't Hoff and Lebel Proposed
Baeyer Strain Theory instable cycloalkanes. The large ring systems involve negative strain hence do not exists. Introduction The bond angles in cyclohexane and higher Van’t Hoff and Lebel proposed tetrahedral cycloalkanes (cycloheptane, cyclooctane, geometry of carbon. The bond angel is of 109˚ cyclononane……..) are not larger than 109.5 28' (or 109.5˚) for carbon atom in tetrahedral because the carbon rings of those compounds geometry (methane molecule). Baeyer are not planar (flat) but they are puckered observed different bond angles for different (Wrinkled). cycloalkanes and also observed some These assumptions are helpful to understand different properties and stability .On this instability of cycloalkane ring systems. basis, he proposed angle strain theory. The theory explains reactivity and stability of Cyclopropane is more prone to cycloalkanes. Baeyer proposed that the undergo ring opening reaction than optimum overlap of atomic orbitals is cyclobutane or cyclopentane achieved for bond angel of 109.5 .In short, it is Cyclopropane is more reactive than ideal bond angle for alkane compounds. cyclobutane and cyclopentane Effective and optimum overlap of atomic orbitals produces maximum bond strength The ring of cyclopropane is triangle. hance stable molecule. All the three angles are of 60 in place of 109.5 (normal bond angle for If bond angles deviate from the ideal carbon atom) to adjust them into then ring produce strain. triangle ring system. Higher the strain higher the In same manner, cyclobutane is instability. square and the bond angles are of 90o in place of 109.5o (normal bond Higher strain increases reactivity and angle for carbon atom) to adjust them increases heat of combustion. -
Cycloalkanes, Cycloalkenes, and Cycloalkynes
CYCLOALKANES, CYCLOALKENES, AND CYCLOALKYNES any important hydrocarbons, known as cycloalkanes, contain rings of carbon atoms linked together by single bonds. The simple cycloalkanes of formula (CH,), make up a particularly important homologous series in which the chemical properties change in a much more dramatic way with increasing n than do those of the acyclic hydrocarbons CH,(CH,),,-,H. The cyclo- alkanes with small rings (n = 3-6) are of special interest in exhibiting chemical properties intermediate between those of alkanes and alkenes. In this chapter we will show how this behavior can be explained in terms of angle strain and steric hindrance, concepts that have been introduced previously and will be used with increasing frequency as we proceed further. We also discuss the conformations of cycloalkanes, especially cyclo- hexane, in detail because of their importance to the chemistry of many kinds of naturally occurring organic compounds. Some attention also will be paid to polycyclic compounds, substances with more than one ring, and to cyclo- alkenes and cycloalkynes. 12-1 NOMENCLATURE AND PHYSICAL PROPERTIES OF CYCLOALKANES The IUPAC system for naming cycloalkanes and cycloalkenes was presented in some detail in Sections 3-2 and 3-3, and you may wish to review that ma- terial before proceeding further. Additional procedures are required for naming 446 12 Cycloalkanes, Cycloalkenes, and Cycloalkynes Table 12-1 Physical Properties of Alkanes and Cycloalkanes Density, Compounds Bp, "C Mp, "C diO,g ml-' propane cyclopropane butane cyclobutane pentane cyclopentane hexane cyclohexane heptane cycloheptane octane cyclooctane nonane cyclononane "At -40". bUnder pressure. polycyclic compounds, which have rings with common carbons, and these will be discussed later in this chapter. -
(12) United States Patent (10) Patent No.: US 9,072,293 B2 Yo0 Et Al
US009072293B2 (12) United States Patent (10) Patent No.: US 9,072,293 B2 Yo0 et al. (45) Date of Patent: Jul. 7, 2015 (54) CYCLOPROPENES AND METHOD FOR 6,452,060 B2 9, 2002 Jacobson APPLYING CYCLOPROPENESTO 6,548.448 B2 4/2003 Kostansek 6,762,153 B2 7/2004 Kostansek et al. AGRICULTURAL PRODUCTS OR CROPS 6,953,540 B2 10/2005 Chong et al. 2001/OO 19995 A1 9, 2001 Sisler (75) Inventors: Sang-Ku Yoo, Gyeonggi-do (KR); Jin 2004/00775O2 A1* 4/2004 Jacobson et al. .............. 504,313 Wook Chung, Seoul (KR) 2004/O192554 A1 9/2004 Kashimura et al. 2005/0065033 A1 3/2005 Jacobson et al. .............. 504,343 (73) Assignee: Erum Biotechnologies Inc., 2008/0286426 A1* 11/2008 Yoo ............................... 426,321 Gyeonggi-Do (KR) FOREIGN PATENT DOCUMENTS (*) Notice: Subject to any disclaimer, the term of this JP 10-94741 4f1998 patent is extended or adjusted under 35 KR 10-2003-0O86982 11, 2003 U.S.C. 154(b) by 0 days. KR 102003OO86982. A * 11, 2003 KR 10-2007-0053113 5/2007 KR 1020070053113 5/2007 (21) Appl. No.: 13/581,797 KR 1020070053113 A * 5, 2007 (22) PCT Filed: Apr. 15, 2011 WO WO O2/068367 9, 2002 OTHER PUBLICATIONS (86). PCT No.: IPRP for related PCT/KR2011/002692 issued on Oct. 23, 2012 and S371 (c)(1), its English translation. (2), (4) Date: Aug. 29, 2012 ISR for related PCT/KR2011/002692 mailed on Jan. 2, 2012 and its English translation. (87) PCT Pub. No.: WO2011/132888 Fumie Sato, et al. “Generation of a Silylethylene-Titanium Alkoxide Complex. -
Strain-Promoted 1,3-Dipolar Cycloaddition of Cycloalkynes and Organic Azides
Top Curr Chem (Z) (2016) 374:16 DOI 10.1007/s41061-016-0016-4 REVIEW Strain-Promoted 1,3-Dipolar Cycloaddition of Cycloalkynes and Organic Azides 1 1 Jan Dommerholt • Floris P. J. T. Rutjes • Floris L. van Delft2 Received: 24 November 2015 / Accepted: 17 February 2016 / Published online: 22 March 2016 Ó The Author(s) 2016. This article is published with open access at Springerlink.com Abstract A nearly forgotten reaction discovered more than 60 years ago—the cycloaddition of a cyclic alkyne and an organic azide, leading to an aromatic triazole—enjoys a remarkable popularity. Originally discovered out of pure chemical curiosity, and dusted off early this century as an efficient and clean bio- conjugation tool, the usefulness of cyclooctyne–azide cycloaddition is now adopted in a wide range of fields of chemical science and beyond. Its ease of operation, broad solvent compatibility, 100 % atom efficiency, and the high stability of the resulting triazole product, just to name a few aspects, have catapulted this so-called strain-promoted azide–alkyne cycloaddition (SPAAC) right into the top-shelf of the toolbox of chemical biologists, material scientists, biotechnologists, medicinal chemists, and more. In this chapter, a brief historic overview of cycloalkynes is provided first, along with the main synthetic strategies to prepare cycloalkynes and their chemical reactivities. Core aspects of the strain-promoted reaction of cycloalkynes with azides are covered, as well as tools to achieve further reaction acceleration by means of modulation of cycloalkyne structure, nature of azide, and choice of solvent. Keywords Strain-promoted cycloaddition Á Cyclooctyne Á BCN Á DIBAC Á Azide This article is part of the Topical Collection ‘‘Cycloadditions in Bioorthogonal Chemistry’’; edited by Milan Vrabel, Thomas Carell & Floris P. -
In This Handout, All of Our Functional Groups Are Presented As Condensed Line Formulas, 2D and 3D Formulas and with Nomenclature Prefixes and Suffixes (If Present)
In this handout, all of our functional groups are presented as condensed line formulas, 2D and 3D formulas and with nomenclature prefixes and suffixes (if present). Organic names are built on a foundation of alkanes, alkenes and alkynes. Those examples are presented first and you need to know those rules. The strategies can be found in Chapter 4 of our textbook (alkanes: pages 93-98, cycloalkanes 102-104, alkenes: pages 104-110, alkynes: pages 112-113 and combinations of all of them 113-115). After introducing examples of alkanes, alkenes, alkynes and combinations of them, the functional groups are presented in order of priority. A few nomenclature examples are provided for each of the functional groups. Examples of the various functional groups are presented on pages 115-135 in the textbook. Two overview pages are on pages 136-137. Some functional groups have a suffix name when they are the highest priority functional group and a prefix name when they are not the highest priority group, and these are added to the skeletal names with identifying numbers and stereochemistry terms (E and Z for alkenes, R and S for chiral centers and cis and trans for rings). Several low priority functional groups only have a prefix name. A few additional special patterns are shown on pages 98-102. The only way to learn this topic is practice (over and over). The best practice approach is to actually write out the names (on an extra piece of paper or on a white board, and then do it again). The same functional groups are used throughout the entire course. -
(12) United States Patent (10) Patent No.: US 7,560,510 B2 Wang Et Al
US007560510B2 (12) United States Patent (10) Patent No.: US 7,560,510 B2 Wang et al. (45) Date of Patent: *Jul. 14, 2009 (54) NANO-SIZED INORGANIC METAL 4,906,695 A 3, 1990 Blizzard et al. PARTICLES, PREPARATION THEREOF, AND 4,920,160 A 4/1990 Chip et al. APPLICATION THEREOF IN IMPROVING 4.942,209 A 7, 1990 Gunesin RUBBER PROPERTIES 5,036,138 A 7, 1991 Stamhuis et al. (75) Inventors: Xiaorong Wang, Hudson, OH (US); 5,066,729 A 1 1/1991 Srayer, Jr. et al. Georg G. A. Böhm, Akron, OH (US) 5,073,498 A 12/1991 Schwartz et al. 5,075,377 A 12/1991 Kawakubo et al. (73) Assignee: Bridgestone Corporation, Tokyo (JP) 5, 120,379 A 6/1992 Noda et al. (*) Notice: Subject to any disclaimer, the term of this 5,130,377 A 7/1992 Trepka et al. patent is extended or adjusted under 35 5,169,914 A 12, 1992 Kaszas et al. U.S.C. 154(b) by 17 days. 5,194,300 A 3/1993 Cheung 5,219,945 A 6/1993 Dicker et al. This patent is Subject to a terminal dis 5,227419 A 7, 1993 Moczygemba et al. claimer. 5,237,015 A 8, 1993 Urban (21) Appl. No.: 11/642,124 5,241,008 A 8, 1993 Hall 5,247,021 A 9/1993 Fujisawa et al. (22) Filed: Dec. 20, 2006 5,256,736 A 10/1993 Trepka et al. 5,262,502 A 11/1993 Fujisawa et al. (65) Prior Publication Data 5,290,873 A 3, 1994 Noda et al. -
Chem 341 • Organic Chemistry I Lecture Summary 10 • September 14, 2007
Chem 341 • Organic Chemistry I Lecture Summary 10 • September 14, 2007 Chapter 4 - Stereochemistry of Alkanes and Cycloalkanes Conformations of Cycloalkanes Cyclic compounds contain something we call Ring Strain. There are three things that contribute to ring strain. Torsional strain (electron repulsion in eclipsing bonds), steric strain (atoms bumping into each other) and angle strain. Angle Strain: the strain due to bond angles being forced to expand or contract from their ideal. Sp3 hybridized atoms want to have bond angles of 109.5°. However, if the rings are very small or very large, there is no way to accommodate this angle. Thus, this increases the energy of the molecule. Heat of Combustion: the amount of heat (energy) released when a molecule burns completely with oxygen. By comparing the heat of combustion of different sized cycloalkanes, their relative energies can be obtained. The fact that the size of the ring has an influence on the total energy of the molecule indicates that there is some degree of instability associated with constraining the rings. This added energy (in addition to what would be expected from carbon and hydrogen combustion per mole) can be attributed to ring strain. n i a r t S g n i R 3 4 5 6 7 8 9 10 11 12 13 14 Ring Size Conformations of Cyclopropane Cyclopropane has a high degree of angle strain due to the highly distorted bond angles. The angle between the carbons is 60°. This cannot be accommodated by sp3-hybridized atoms. Thus, the 60° bonds actually are bent sigma bonds.