Isomers Have Same Molecular Formula, but Different Structures
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Chiral Separation of Rac-Propylene Oxide on Penicillamine Coated Gold Nps
nanomaterials Article Chiral Separation of rac-Propylene Oxide on Penicillamine Coated Gold NPs Nisha Shukla 1,2, Zachary Blonder 2 and Andrew J. Gellman 2,3,* 1 Institute of Complex Engineered Systems, Carnegie Mellon University, Pittsburgh, PA 15213, USA; [email protected] 2 Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA; [email protected] 3 W.E. Scott Institute for Energy Innovation, Carnegie Mellon University, Pittsburgh, PA 15213, USA * Correspondence: [email protected] Received: 16 July 2020; Accepted: 20 August 2020; Published: 30 August 2020 Abstract: The surfaces of chemically synthesized spherical gold NPs (Au-NPs) have been modified using chiral L- or D-penicillamine (Pen) in order to impart enantioselective adsorption properties. These chiral Au-NPs have been used to demonstrate enantioselective adsorption of racemic propylene oxide (PO) from aqueous solution. In the past we have studied enantioselective adsorption of racemic PO on L- or D-cysteine (Cys)-coated Au-NPs. This prior work suggested that adsorption of PO on Cys-coated Au-NPs equilibrates within an hour. In this work, we have studied the effect of time on the enantioselective adsorption of racemic PO from solution onto chiral Pen/Au-NPs. Enantioselective adsorption of PO on chiral Pen/Au-NPs is time-dependent but reaches a steady state after ~18 h at room temperature. More importantly, L- or D-Pen/Au-NPs are shown to adsorb R- or S-PO enantiospecifically and to separate the two PO enantiomers from racemic mixtures of RS-PO. Keywords: chiral; nanoparticles; enantioselective adsorption; penicillamine; cysteine 1. Introduction Chirality has attracted enormous interest in the field of chemistry due to the enantiospecific responses of living organisms to the two enantiomers of chiral compounds that they have ingested. -
II. Stereochemistry 5
B.Sc.(H) Chemistry Semester - II Core Course - III (CC-III) Organic Chemistry - I II. Stereochemistry 5. Physical and Chemical Properties of Stereoisomers Dr. Rajeev Ranjan University Department of Chemistry Dr. Shyama Prasad Mukherjee University, Ranchi 1 Syllabus & Coverage Syllabus II Stereochemistry: Fischer Projection, Newmann and Sawhorse Projection formulae and their interconversions. Geometrical isomerism: cis–trans and syn-anti isomerism, E/Z notations with Cahn Ingold and Prelog (CIP) rules for determining absolute configuration. Optical Isomerism: Optical Activity, Specific Rotation, Chirality/Asymmetry, Enantiomers, Molecules with two or more chiral-centres, Distereoisomers, Meso structures, Racemic mixture. Resolution of Racemic mixtures. Relative and absolute configuration: D/L and R/S designations. Coverage: 1. Types of Isomers : Comparing Structures 2. Optical Activity 3. Racemic Mixtures : Separation of Racemic Mixtures 4. Enantiomeric Excess and Optical Purity 5. Relative and Absolute Configuration 6. Physical and Chemical Properties of Stereoisomers 2 Stereochemistry Types of Isomers Dr. Rajeev Ranjan 3 Stereochemistry Determining the Relationship Between Two Non-Identical Molecules Dr. Rajeev Ranjan 4 Stereochemistry Comparing Structures: Are the structures connected the same? yes no Are they mirror images? Constitutional Isomers yes no Enantiomers Enantiomers Is there a plane of symmetry? All chiral centers will be opposite between them. yes no Meso Diastereomers superimposable Dr. Rajeev Ranjan 5 Stereochemistry Optical Activity: • The chemical and physical properties of two enantiomers are identical except in their interaction with chiral substances. • The physical property that differs is the behavior when subjected to plane-polarized light ( this physical property is often called an optical property). • Plane-polarized (polarized) light is light that has an electric vector that oscillates in a single plane. -
Effect of the Enantiomeric Ratio of Eutectics on the Results and Products of the Reactions Proceeding with the Participation Of
Perspective Effect of the Enantiomeric Ratio of Eutectics on the Results and Products of the Reactions Proceeding with the Participation of Enantiomers and Enantiomeric Mixtures Emese Pálovics *, Dorottya Fruzsina Bánhegyi and Elemér Fogassy Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, 1521 Budapest, Hungary; [email protected] (D.F.B.); [email protected] (E.F.) * Correspondence: [email protected]; Tel.: +36-1-4632101 Received: 3 August 2020; Accepted: 14 September 2020; Published: 21 September 2020 Abstract: This perspective is focused on the main parameters determining the results of crystallization of enantiomers or enantiomeric mixtures. It was shown that the ratio of supramolecular and helical associations depends on the eutectic composition of the corresponding enantiomeric mixture. The M and P ratios together with the self-disproportionation (SDE) of enantiomers define the reaction of the racemic compound with the resolving agent. Eventually, each chiral molecule reacts with at least two conformers with different degrees of M and P helicity. The combined effect of the configuration, charge distribution, constituent atoms, bonds, flexibility, and asymmetry of the molecules influencing their behavior was also summarized. Keywords: chiral molecules; enantiomeric separation; self-disproportionation of enantiomers; supramolecular associations; helical structure; eutectic composition 1. Introduction The preparation of asymmetric (chiral) compounds (enantiomers) is one of the main goals of research, industry and medicine. The preparation of a given enantiomer is possible in several ways, for example by selective synthesis, which requires the separation of the chiral catalyst or the enantiomers of the racemic compound, and in which case a resolving agent (like a chiral catalyst) may be required. -
Enantioselective Synthesis of the (1S,5R)-Enantiomer of Litseaverticillols a and B
Biosci. Biotechnol. Biochem., 70 (10), 2564–2566, 2006 Note Enantioselective Synthesis of the (1S,5R)-Enantiomer of Litseaverticillols A and B y Akira MORITA, Hiromasa KIYOTA, and Shigefumi KUWAHARA Laboratory of Applied Bioorganic Chemistry, Graduate School of Agricultural Science, Tohoku University, Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan Received May 8, 2006; Accepted May 31, 2006; Online Publication, October 7, 2006 [doi:10.1271/bbb.60253] An enantioselective synthesis of the (1S,5R)-enan- which have recently culminated in the first enantiose- tiomer of litseaverticillols A and B was accomplished in lective total synthesis of (1R,5S)-(À)-1 and (1R,5S)-(À)- line with our previously reported synthetic pathway for 2.4) In this note, we describe the synthesis of their their (1R,5S)-enantiomer. The use of ‘‘EtSCeCl2’’ pre- enantiomers directed toward an evaluation of the differ- pared from EtSLi and CeCl3, instead of previously ence in biological activity between the enantiomers of employed EtSLi itself, for the formation of thiol ester litseaverticillols A and B. intermediates prevented any undesirable epimerization Our synthesis of (1S,5R)-1 and (1S,5R)-2 basically occurring in the process. followed our previous synthesis of their corresponding enantiomers, (1R,5S)-1 and (1R,5S)-2, respectively,4) Key words: litseaverticillol; enantioselective synthesis; except that (R)-4-benzyloxazolidin-2-one was employed sesquiterpenoid; anti-HIV as the source of chirality, instead of its (S)-form used in the previous synthesis. Homogeranic -
Lecture 3: Stereochemistry and Drugs Key Objectives: 1
Lecture 3: Stereochemistry and drugs Key objectives: 1. Be able to explain the role of stereochemistry in drug action or metabolism 2. Be able to identify a chiral center (or centers) in a drug 3. Be able to explain the difference between enantiomers and diastereomers Value of chirality and stereochemistry: Chirality as expressed through stereoisomers increases the specificity of molecule recognition and signaling. Like a key in a lock, or a hand in a glove. Some useful definitions: Chirality (and chiral centers): An object (such as a molecule) that is asymmetric and therefore not superimposable on its own image. Chiral centers are the most common features within molecules that give rise to chirality. Stereoisomer: A molecule that possesses at least one chiral center (or center of chirality). Enantiomers: A type of stereoisomer that exists in mirror image forms. See Figure 1. Diastereomers: A type of stereoisomer that possesses more than one chiral center. Stereospecific: A term used to describe a stereochemical property that one isomer possesses but the other does not. For example, the stereospecific metabolism of the S-enantiomer of a compound by an enzyme but the R-enantiomer is not metabolized by that enzyme. Stereoselective: A term used to describe a stereochemical property that is shared by both stereoisomers, but the property is greater in one isomer than the other. For example, the stereoselective binding of the R-enantiomer for a receptor indicates that the S-enantiomer also binds but not as avidly as the R-enantiomer. Enantiomers Figure 1: For enantiomers, many times we use the example of our left and right hands to demonstrate their asymmetry. -
Diastereomers Diastereomers
Diastereomers Diastereomers: Stereoisomers that are not mirror images. enantiomer (R) (S) (S) (R) diastereomers diastereomer diastereomer enantiomer (R) (S) (R) (S) Diastereomers Diastereomers: Stereoisomers that are not mirror images. (R) enantiomer (S) (S) (R) diastereomer To draw the enantiomer of a molecule with chiral centers, invert stereochemistry at all chiral centers. (R) To draw a diastereomer of a molecule (R) with chiral centers, invert stereochemistry at only some chiral centers. Meso Compounds Meso: A molecule that contains chiral centers, but is achiral. 3 Are these molecules chiral? (R) (S) (These are diff eren t f rom th e 3 molecules I just showed; they have 2 -Cl’s, rather than 1 -Cl & 1 -OH. enantiomer (R) (S) (R) (S) These molecules are chiral mirror images of one another. (R,R) and (S,S) are not the same. Meso Compounds Meso: A molecule that contains chiral centers, but is achiral. 3 enantiomer ? (R) (S) (S) (R) no! 3 same molecule! enantiomer (R) (S) (R) (S) Meso Compounds Meso: A molecule that contains chiral centers, but is achiral. 3 enantiomer ? (R) (S) (S) (R) no! 3 same molecule! If a molecule • contains the same number of (R) and (S) stereocenters, and • those stereocenters have identical groups attached, then the molecule is achiral and meso. Meso Compounds Meso: A molecule that contains chiral centers, but is achiral. 3 same molecule (R) (S) (S) (R) 3 meso diastereomers meso diastereomer diastereomer enantiomer (R) (S) (R) (S) chiral chiral Properties of Enantiomers Most physical properties of enantiomers are identical. diethyl-(R,R)-tartrate diethyl-(S,S)-tartrate boiling point 280 °C 280 °C melting point 19 °C 19 °C density 1.204 g/mL 1.204 g/mL refractive index 1.447 1.447 i.e., chirality does not affect most physical properties. -
Enantiomers & Diastereomers
Chapter 5 Stereochemistry Chiral Molecules Ch. 5 - 1 1. Chirality & Stereochemistry An object is achiral (not chiral) if the object and its mirror image are identical Ch. 5 - 2 A chiral object is one that cannot be superposed on its mirror image Ch. 5 - 3 1A. The Biological Significance of Chirality Chiral molecules are molecules that cannot be superimposable with their mirror images O O ● One enantiomer NH causes birth defects, N O the other cures morning sickness O Thalidomide Ch. 5 - 4 HO NH HO OMe Tretoquinol OMe OMe ● One enantiomer is a bronchodilator, the other inhibits platelet aggregation Ch. 5 - 5 66% of all drugs in development are chiral, 51% are being studied as a single enantiomer Of the $475 billion in world-wide sales of formulated pharmaceutical products in 2008, $205 billion was attributable to single enantiomer drugs Ch. 5 - 6 2. Isomerisom: Constitutional Isomers & Stereoisomers 2A. Constitutional Isomers Isomers: different compounds that have the same molecular formula ● Constitutional isomers: isomers that have the same molecular formula but different connectivity – their atoms are connected in a different order Ch. 5 - 7 Examples Molecular Constitutional Formula Isomers C4H10 and Butane 2-Methylpropane Cl Cl C3H7Cl and 1-Chloropropane 2-Chloropropane Ch. 5 - 8 Examples Molecular Constitutional Formula Isomers CH O CH C H O OH and 3 3 2 6 Ethanol Methoxymethane O OCH and 3 C H O OH 4 8 2 O Butanoic acid Methyl propanoate Ch. 5 - 9 2B. Stereoisomers Stereoisomers are NOT constitutional isomers Stereoisomers have their atoms connected in the same sequence but they differ in the arrangement of their atoms in space. -
Chapter 4: Stereochemistry Introduction to Stereochemistry
Chapter 4: Stereochemistry Introduction To Stereochemistry Consider two of the compounds we produced while finding all the isomers of C7H16: CH3 CH3 2-methylhexane 3-methylhexane Me Me Me C Me H Bu Bu Me Me 2-methylhexane H H mirror Me rotate Bu Me H 2-methylhexame is superimposable with its mirror image Introduction To Stereochemistry Consider two of the compounds we produced while finding all the isomers of C7H16: CH3 CH3 2-methylhexane 3-methylhexane H C Et Et Me Pr Pr 3-methylhexane Me Me H H mirror Et rotate H Me Pr 2-methylhexame is superimposable with its mirror image Introduction To Stereochemistry Consider two of the compounds we produced while finding all the isomers of C7H16: CH3 CH3 2-methylhexane 3-methylhexane .Compounds that are not superimposable with their mirror image are called chiral (in Greek, chiral means "handed") 3-methylhexane is a chiral molecule. .Compounds that are superimposable with their mirror image are called achiral. 2-methylhexane is an achiral molecule. .An atom (usually carbon) with 4 different substituents is called a stereogenic center or stereocenter. Enantiomers Et Et Pr Pr Me CH3 Me H H 3-methylhexane mirror enantiomers Et Et Pr Pr Me Me Me H H Me H H Two compounds that are non-superimposable mirror images (the two "hands") are called enantiomers. Introduction To Stereochemistry Structural (constitutional) Isomers - Compounds of the same molecular formula with different connectivity (structure, constitution) 2-methylpentane 3-methylpentane Conformational Isomers - Compounds of the same structure that differ in rotation around one or more single bonds Me Me H H H Me H H H H Me H Configurational Isomers or Stereoisomers - Compounds of the same structure that differ in one or more aspects of stereochemistry (how groups are oriented in space - enantiomers or diastereomers) We need a a way to describe the stereochemistry! Me H H Me 3-methylhexane 3-methylhexane The CIP System Revisited 1. -
Chirality and Enantiomers
16.11.2010 Bioanalytics Part 5 12.11.2010 Chirality and Enantiomers • Definition: Optical activity • Properties of enantiomers • Methods: – Polarimetry – Circular dichroism • Nomenclature • Separation of enantiomers • Determination of enantiomeric excess (ee) Determination of absolute configuration • Enantiomeric ratio (E‐value) 1 16.11.2010 Definitions Enantiomers: the two mirror images of a molecule Chirality: non‐superimposable mirror‐images •Depends on the symmetry of a molecule •Point‐symmetry: asymmetric C, Si, S, P‐atoms •Helical structures (protein α‐helix) Quarz crystals snail‐shell amino acids Properties of Enantiomers – Chemical identical – Identical UV, IR, NMR‐Spectra – Differences: • Absorption and refraction of circular polarized light is different – Polarimetry, CD‐spectroscopy • Interaction with other chiral molecules/surfaces is different – Separation of enantiomers on chiral columns (GC, HPLC) 2 16.11.2010 Chiral compounds show optical activity A polarimeter is a device which measures the angle of rotation by passing polarized light through an „optical active“ (chiral) substance. Interaction of light and matter If light enters matter, its intensity (amplitude), polarization, velocity, wavelength, etc. may alter. The two basic phenomena of the interaction of light and matter are absorption (or extinction) and a decrease in velocity. 3 16.11.2010 Interaction of light and matter Absorption means that the intensity (amplitude) of light decreases in matter because matter absorbs a part of the light. (Intensity is the square of amplitude.) Interaction of light and matter The decrease in velocity (i.e. the slowdown) of light in matter is caused by the fact that all materials (even materials that do not absorb light at all) have a refraction index, which means that the velocity of light is smaller in them than in vacuum. -
Magnetic Combined Cross-Linked Enzyme Aggregates of Ketoreductase and Alcohol Dehydrogenase
catalysts Article Magnetic Combined Cross-Linked Enzyme Aggregates of Ketoreductase and Alcohol Dehydrogenase: An Efficient and Stable Biocatalyst for Asymmetric Synthesis of (R)-3-Quinuclidinol with Regeneration of Coenzymes In Situ Yuhan Chen 1, Qihua Jiang 1, Lili Sun 1, Qiang Li 2, Liping Zhou 1, Qian Chen 1, Shanshan Li 1, Mingan Yu 1 and Wei Li 1,3,* 1 Department of Medicinal Chemistry, School of Pharmacy, Chongqing Medical University, Chongqing 400016, China; [email protected] (Y.C.); [email protected] (Q.J.); [email protected] (L.S.); [email protected] (L.Z.); [email protected] (Q.C.); [email protected] (S.L.); [email protected] (M.Y.) 2 Chongqing Key Laboratory of Medicinal Resources in the Three Gorges Reservoir Region, School of Biological & Chemical engineering, Chongqing University of Education, Chongqing 400067, China; [email protected] 3 Chongqing Key Laboratory of Biochemistry and Molecular Pharmacology, Chongqing Medical University, Chongqing 400016, China * Correspondence: [email protected]; Tel.: +86-23-6848-5161 Received: 14 July 2018; Accepted: 30 July 2018; Published: 15 August 2018 Abstract: Enzymes are biocatalysts. In this study, a novel biocatalyst consisting of magnetic combined cross-linked enzyme aggregates (combi-CLEAs) of 3-quinuclidinone reductase (QNR) and glucose dehydrogenase (GDH) for enantioselective synthesis of (R)-3-quinuclidinolwith regeneration of cofactors in situ was developed. The magnetic combi-CLEAs were fabricated with the use of ammonium sulfate as a precipitant and glutaraldehyde as a cross-linker for direct immobilization of QNR and GDH from E. coli BL(21) cell lysates onto amino-functionalized Fe3O4 nanoparticles. The physicochemical properties of the magnetic combi-CLEAs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and magnetic measurements. -
Preferential Crystallization of a Racemic Compound Via Its Conglomerate Co-Crystals
Preferential crystallization of a racemic compound via its conglomerate co-crystals Master Thesis Oscar F. Villamil R August 24th 2016 Faculty of 3ME Department: Process & Energy Section: Intensified Reaction & Separation Systems Graduation Committee Ir. W. Li PDeng Dr. ir. H.J.M Kramer Dr. ir. H.W.Nugteren Dr. ir. A. van der Heijden 1 Abstract Preferential crystallization, as a powerful chiral resolution technique, is intrinsically limited to chiral molecules that crystallize as conglomerates. Many studies have been conducted on using chemical reactions to convert the target molecules, which originally form racemic compounds, into conglomerate-forming derivatives salts or by creating solvate, for the application of preferential crystallization. Up to this date conglomerate co-crystals of racemic compounds have never been applied as the intermediate for chiral resolution. In this study, preferential crystallization of the model compound Ibuprofen (IBU), originally a racemic compound, was carried out via its conglomerate co-crystal with 2,4-bipyridine ethylene (BPE) in heptane. Suitable operation conditions were selected based on pseudo- binary phase diagram of the model compound system constructed under different IBU-BPE ratio. A unique measurement method combining polarimeter and Nuclear Magnetic Resonance (NMR) measurements was developed to identify the enantiopurity and the yield of the final product, which was a mixture of racemic IBU and IBU-BPE co-crystals, a likely result from this complex system. With respect to the results, preferential crystallization of IBU was successfully performed by slowly cooling down a saturated solution of racemic IBU-BPE, initially at T=57.5°C, after seeding it with S-IBU/BPE crystals to T=53°C with a cooling rate of 0.3°C/min. -
Polarimetric Detection of Enantioselective Adsorption by Chiral Au Nanoparticles – Effects of Temperature, Wavelength and Size
Nanomaterials and Nanotechnology ARTICLE Polarimetric Detection of Enantioselective Adsorption by Chiral Au Nanoparticles – Effects of Temperature, Wavelength and Size Invited Article Nisha Shukla2, Nathaniel Ondeck1, Nathan Khosla1, Steven Klara1, Alexander Petti1 and Andrew Gellman1* 1 Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA 2 Institute of Complex Engineered Systems, Carnegie Mellon University, Pittsburgh, PA, USA * Corresponding author(s) E-mail: [email protected] Received 01 November 2014; Accepted 07 January 2015 DOI: 10.5772/60109 © 2015 The Author(s). Licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract 1. Introduction R- and S-propylene oxide (PO) have been shown to interact The importance of chirality arises from the need of the enantiospecifically with the chiral surfaces of Au nanopar‐ pharmaceutical industry, and other producers of bioactive ticles (NPs) modified with D- or L-cysteine (cys). This compounds, for chemical processes that are enantioselec‐ enantiospecific interaction has been detected using optical tive and thereby produce enantiomerically pure chiral polarimetry measurements made on solutions of the D- or products. [1-4] This is one of the most challenging forms of L-cys modified Au (cys/Au) NPs during addition of chemical synthesis and is critical to the performance of racemic PO. The selective adsorption of one enantiomer of bioactive chiral products. Ingestion of the two enantiomers the PO onto the cys/Au NP surfaces results in a net rotation of a chiral compound by a living organism can result in of light during addition of the racemic PO to the solution.