CHAPTER 5. Stereoisomers
|
|
- Dayna Cross
- 6 years ago
- Views:
Transcription
1 CHAPTER 5 Stereoisomers
2 We have already covered two kinds of isomerism: Constitutional Isomers (structural isomers) Stereoisomers
3 Examples of Constitutional Isomers: Examples of Stereoisomers:
4 Another type of stereoisomerism is called mirror-image stereoisomerism. Mirror-image related stereoisomers are said to be left-handed and right-handed and occur when a molecule and its mirror image are non-superimposable.
5 5-1 Chiral Molecules The radical bromination of butane to form 2-bromobutane appears to yield a single product:
6 Chiral molecules cannot be superimposed on their mirror images. The two 2-bromobutane molecules formed by the radical bromination of butane are actually nonsuperimposable and are therefore not identical. A molecule that is not superimposible on its mirror image is said to be chiral. In this case each isomer is called an enantiomer.
7 Compounds whose mirror images are superimposable are called achiral. Examples of chiral and achiral molecules: Above all, the chiral examples contain an atom that is connected to 4 different substituent groups. This atom is called an asymmetric atom or a stereocenter. Often, asymmetric atoms are marked with an asterisk. Molecules having one stereocenter are always chiral.
8 The symmetry in molecules helps to distinguish chiral structures from achiral ones. For most organic molecules, a sufficient test for chirality is absence of a plane of symmetry (mirror plane). A mirror plane is one that bisects the molecule in such a way that the half of the molecule on one side of the plane is the mirror image of the half on the other side of the plane. Methane has 6 planes of symmetry, chloromethane has 3, dichloromethane 2, bromochloromethane 1, and bromochlorofluoromethane none:
9 5-2 Optical Activity Enantiomers cannot be distinguished on the basis of their physical properties, such as boiling points, melting points, and densities. Enantiomers can be distinguished by the way they interact with plane-polarized light. When plane-polarized light is passed through a sample of one of the enantiomers, the plane of polarization is rotated either clockwise or counterclockwise. When the experiment is repeated with the other enantiomer, the plane-polarized light is rotated an equal amount, but in the opposite direction. If facing the light source: Clockwise rotation: enantiomer is dextrorotary (+) Counterclockwise rotation: enantiomer is levorotary (-) This interaction with light is called optical activity and enantiomers are often called optical isomers.
10 Optical rotation is measured with a polarimeter. Light is electromagnetic radiation that oscillates perpendicular to its direction of motion. The oscillation of light can be resolved into two perpendicular components. When light is passed through a polarizer, only one of the two perpendicular components of light is passed through. This light is referred to as plane-polarized light.
11 When plane-polarized light interacts with a chiral molecule, the plane of polarization of the light is rotated to the left or right. This effect is called optical rotation and the molecule is said to be optically active. Optical activity is measured using a polarimeter. This device contains a light source, a polarizer to produce the plane-polarized light, a sample cell, and an analyzer to determine the amount of rotation.
12 The measured rotation (in degrees) is the observed optical rotation, α, of the sample. The value of α depends upon: Structure of the chiral molecule Concentration of the chiral molecule Length of the sample cell Wavelength of the light Solvent used Temperature
13 The specific rotation [α] of a sample is defined for each chiral molecule (the value is solvent dependent): Specific rotation is a physical constant for a substance, as is melting point, boiling point, density, etc.
14 Examples of specific rotations:
15 Optical rotation indicates enantiomeric composition. A racemic mixture is a mixture of equal amounts of the + and enantiomers of a chiral compound. It shows no net rotation of plane-polarized light. When one enantiomer equilibrates with its mirror image, the process is called racemization. When one of the two enantiomers of a chiral compound is present in a mixture in excess over the other, there will be a net rotation of plane-polarized light. A 50% enantiomer excess would be defined as a mixture of 75% one enantiomer and 25% of the other (50%+ with 25%+ and 25%-). The mixture would be called 50% optically pure. The optical purity of an enantiomer is defined:
16 5-3 Absolute Configuration: R-S Sequence Rules X-ray diffraction can establish the absolute configuration. The absolute configuration of an enantiomer is the actual spatial arrangement of the substituent groups around the chiral centers. There is no straightforward correlation between the absolute configuration of an enantiomer and the sign of rotation of the molecule. The absolute configuration of an enantiomer can be determined through single crystal X-ray diffraction analysis or through chemical correlation to a molecule whose absolute configuration has already been determined.
17 Stereocenters are labeled R or S. The convention for naming enantiomers unambiguously was developed by R.S. Cahn, C. Ingold, and V. Prelog. The four substituents around the chiral carbon must be first ranked in order of decreasing priority. a highest priority b second-highest priority c third-highest priority d lowest priority When the molecule is positioned with the lowest-priority substituent away from the viewer, the remaining three substituents will be arranged in either a clockwise or counterclockwise direction.
18 If the progression from a to b to c is clockwise, the configuration at the stereocenter is named S (sinister) otherwise the configuration is named R (rectus) The R or S is added as a prefix in parentheses to the name of the chiral compound. (R)-2-bromobutane (S)-2,3-dihydroxypropanal (R,S)-bromochlorofluoromethane (a racemic mixture) If known, the sign of rotation of plane-polarized light may also be added, however, there is no correlation between R,S and +,-: (R)-(+)-2,3-dihydroxypropanal.
19 Sequence rules assign priorities to substituents. Rule 1: Look first at the atoms directly attached to the stereocenter. Precedence is in order of highest atomic number. Hydrogen is always the lowest precedence. A higher-mass isotope takes precedence over a lower-mass isotope.
20 Rule 2: If two atoms are of the same precedence using rule 1, proceed along the two respective substituent chains until you reach a point of difference.
21 Verify these two examples:
22 Rule 3: Double and triple bonds are treated as if they are single and the atoms in them are duplicated or triplicated at each end by the respective atoms at the other end of the multiple bond. Verify these assignments:
23 5-4 Fischer Projections Fischer projection formulas represent 3-D tetrahedral carbon atoms and their substituents in two dimensions. The molecule is drawn in the form of a cross. The tetrahedral carbon is in the plane of the paper at the center of the cross. Atoms connected to the tetrahedral carbon by horizontal bonds are behind the plane of the paper. Atoms connected to the tetrahedral carbon by vertical bonds are in front of the plane of the paper.
24 There is more than one correct way to draw a Fischer projection:
25 Rotating a Fischer projection may or may not change the absolute configuration. Rotating a Fisher projection formula by 90 o converts the structure into that of the enantiomer of the molecule originally represented. Rotating a Fisher projection formula by 180 o keeps the same enantiomer.
26 Exchanging substituents in a Fischer projection also changes the absolute configuration. To compare a Fischer projection to another in a different orientation in order to see if they represent the same enantiomer: Exchange any two substituents. This turns the molecule into its mirror image. Exchange another two substituents. This then turns the molecule back into the original enantiomer. Using a series of exchanges, convert one Fisher formula into the other. If an odd number of exchanges are required, the two projection formulas represent different enantiomers. If an even number of exchanges are required, the two projection formulas represent the same enantiomer.
27 Fischer projections tell us the absolute configuration. Draw any correct Fischer projection formula of a chiral center. Assign priorities to all of the substituents. Using two consecutive substituent exchanges (to preserve the chirality of the Fischer formula), place group d (lowest priority) on the top. If the a,b,c groups are now arranged in a clockwise order, the enantiomer is R: if in a counterclockwise order, the enantiomer is S.
28 5-5 Molecules Incorporating Several Stereocenters: Diastereomers Two stereocenters can give four stereoisomers: chlorination of 2-bromobutane at C3. Consider the chlorination of 2- bromobutane. Several products are formed, but consider only the 2- bromo-3-chlorobutane. A second stereocenter is formed by the addition of the chlorine atom.
29 The possible combinations are RR, RS, SR, and SS.
30 Because all of the horizontal bonds in a Fischer projection formula point towards the viewer and all vertical bonds away from the viewer, a Fischer projection formula represents the molecule in its eclipsed conformation. In order to convert a Newman or dashed-wedged representation into a Fischer representation, first rotate the molecule to form an eclipsed rotomer. Treat each stereocenter separately and regard the group containing the other stereocenter as a simple substituent.
31 When a chiral molecule has two stereocenters, four stereoisomers are possible: RR, RS, SR, and SS. The RR and SS isomers are mirror images of each other and are therefore enantiomers. The RS and SR isomers are also mirror images of each other and are enantiomers. The RR and RS stereoisomers are not mirror images of each other; nor are the SS and SR stereoisomers. Stereoisomers not related as object and mirror image are called diastereomers. Diastereomers are distinct molecules with different physical and chemical properties. They can be separated by fractional distillation, crystallization, or chromatography. They have different melting points, boiling points, densities, and specific rotations.
32 Cis and trans isomers are cyclic diastereomers. Consider 1-bromo-2-chlorocyclobutane: There are 4 stereoisomers: RR, SS, RS, and SR. The two cis isomers, SR and RS, are enantiomers and the two trans isomers, RR and SS are enantiomers. A cis isomer and a trans isomer are diastereomers of each other.
33 More than two stereocenters means still more stereoisomers. A compound containing 3 stereocenters will exist as 8 stereoisomers which can be grouped into 4 pairs of enantiomers: RRR SSS SRR RSS RSR SRS RRS SSR In general, a compound having n stereocenters can have a maximum of 2 n stereoisomers.
34 5-6 Meso Compounds Two identically substituted stereocenters give rise to only three stereoisomers. Consider the radical bromination of 2-bromobutane: Since there are 2 chiral centers in the product, we might expect 4 distinct stereoisomers: RR, RS, SR, and SS. These could then be organized into enantiomeric pairs: RR SS and RS SR.
35 A closer look at the RS and SR pair of molecules, however, shows that they are superimposable molecules and are therefore identical. A compound containing 2 or more stereocenters that is superimposable with its mirror image is called a meso compound. Meso compounds contain an internal mirror plane which divides the two halves of the molecule which are mirror images of each other.
36 The presence of a mirror plane in any energetically accessible conformation of a molecule is sufficient to make it achiral. 2,3-Dibromobutane exists as three stereoisomers only: a pair of enantiomers and an achiral meso diastereomer. Examples of meso compounds having multiple chiral centers:
37 Cyclic compounds may also be meso. 1,2-Dicyclobutane exists in the cis and the trans form. The cis form, however, contains a mirror plane and is therefore an achiral meso compound. For the purpose of identifying a mirror plane, cyclic compounds can usually be treated as if the ring were planar since the out-ofplane conformers are all generally interconvertable at room temperature.
38 5-7 Stereochemistry in Chemical Reactions The radical mechanism explains why the bromination of butane results in a racemate. When a hydrogen atom is extracted from butane by an attacking bromine atom, it does not matter which hydrogen is extracted, an achiral planar sp 2 radical is formed: The two lobes of the p orbital are equally susceptible to attack by bromine in the second step. The two transition states are energetically equivalent to each other, so equal amounts of the two enantiomeric products are formed.
39 The formation of chiral compounds from achiral reagents yields racemates (optically inactive reactants yield optically inactive products).
40 The presence of a stereocenter affects the outcome of the reaction: chlorination of (S)-2-bromobutane. Chlorination of (S)-2-bromobutane at a terminal methyl group can proceed at either C1 or at C4: Both products are optically active. The original stereocenter remains unchanged. In the case of C1 chlorination, the sequence of priorities about the stereocenter changes, which changes the configuration at C2 from S to R. In the case of C4 chlorination, the carbon chain must be renumbered to maintain the lowest possible substituent numbering.
41 Chlorination of (S)-2-bromobutane at C2, the stereocenter, leads to 2-bromo-2-chlorobutane. The molecule remains chiral, however a racemic mixture is formed. Hydrogen abstraction at C2 leads to a planar, sp 2 -hybridized, achiral radical. Chlorination occurs equally at either lobe of the p orbital leading to equal amounts of the R and S enantiomers and thus a racemic mixture.
42 Chlorination of (S)-2-bromobutane at C3, forms a second stereocenter and gives rise to diastereomers In this case, the two faces of the radical transition state are not mirror images of each other, due to the stereocenter at C2. Attack by chlorine at the two faces of the radical will occur at different rates (due to steric reasons) and the two diastereomers are formed at different rates.
43 Stereoselectivity is the preference for one stereoisomer. A reaction that favors the formation of one of several possible stereoisomeric products is said to be stereoselective. Chlorination of (S)-2-bromobutane at C3 is stereoselective, whereas chlorination at C2 is not (a racemate is formed). 100% stereoselectivity is usually obtained in nature when enzymes (chiral molecules themselves) convert achiral compounds into chiral ones.
44 5-8 Resolution: Separation of Enantiomers Pure enantiomers can be obtained by first synthesizing a racemic mixture and then separating the enantiomers formed by a process called resolution. Resolution is best carried out by converting a racemate into a mixture of diastereomers by adding an enantiomerically pure reagent. The resulting diastereomers can then be separated by standard techniques. Each pure diastereomer can then be separated into one of the original enantiomeric molecules and the optically active reagent, which can be used again to resolve further racemic mixtures.
45 A popular reaction employed in the resolution of racemic mixtures is salt formation between acids and bases. (+) Tartaric acid can be used to resolve racemic amines. Chiral chromatography can be used to resolve racemic mixtures without first isolating diastereomers. In this method, an optically active compound is attached to a solid support in a column, and the racemic mixture is allowed to pass through it. Each of the two enantiomeric molecules in the mixture will interact differently with the attached chiral molecule and will have different retention times on the column.
46 5 Important Concepts 1. Isomers Same molecular formula, different compounds: Constitutional Individual atoms are connected differently Stereoisomers Same connectivity, different 3D arrangement. Mirror-Image Stereoisomers Related as image 2. Chiral Molecule Not superimposable on its mirror image 3. Stereocenter Carbon atom bearing 4 different substituents 4. Enantiomers Two stereoisomers, each a nonsuperimposable mirror image of the other
47 5 Important Concepts 5. Racemate A one-to-one mixture of enantiomers 6. Mirror Plane Chiral molecules cannot contain a mirror plane. 7. Diastereomers Stereoisomers not related to each other as mirror images (i.e. cis/trans). 8. Two Stereocenters In A Molecule Create up to 4 stereoisomers: 2 diastereomerically related pairs. If the 2 stereocenters generate a mirror plane in the molecule, the molecule is known as a meso compound and is achiral. 9. Physical Properties of Stereoisomers Most are the same except for the rotation of plane-polarized light. One enantiometer rotates the plane of polarization to the right, the other to the left. This rotation is expressed as the specific rotation [α].
48 5 Important Concepts 10. Absolute Configuration Determined by X-ray diffraction. Assignment of R or S, as determined by the Cahn, Ingold, and Prelog sequence rules 11. Fischer Projections Standard 2-D representation of 3-D molecules containing stereocenters 12. Radical Halogenation Can introduce chirality into an achiral compound. Racemic mixtures are often produced. 13. Radical Halogenation of a Chiral Molecule Containing 1 Stereocenter Gives a racemate if the reaction occurs at the stereocenter Gives 2 diastereomers in unequal amounts if the reaction occurs elsewhere
49 5 Important Concepts 14. Stereoselectivity Preference for the formation of one stereoisomer when several are possible 15. Resolution Separation of enantiomers Reaction with a pure enantiomer of a second chiral compound and separation of the diastereomers Chiral chromatography
Chemistry 123: Physical and Organic Chemistry Topic 1: Organic Chemistry
Concept Check: Topic 1: Conformation Winter 2009 Page 112 Concept Check: Topic 1: Conformation Winter 2009 Page 113 1 STEREOCHEMISTRY Winter 2009 Page 114 We have already covered two kinds of isomerism:
More information240 Chem. Stereochemistry. Chapter 5
240 Chem Stereochemistry Chapter 5 1 Isomerism Isomers are different compounds that have the same molecular formula. Constitutional isomers are isomers that differ because their atoms are connected in
More informationCH 3 C 2 H 5. Tetrahedral Stereochemistry
Ch 5 Tetrahedral Stereochemistry Enantiomers - Two non-superimposable mirror image molecules - They are stereoisomers with the same atoms and bonds, but different spatial geometries. - The two molecules
More informationStereochemistry. In organic chemistry, subtle differences in spatial arrangements can give rise to prominent effects.
Stereochemistry This is study of the 3 dimensional arrangement in space of molecules. In organic chemistry, subtle differences in spatial arrangements can give rise to prominent effects. E.g. the isomers
More informationChapter 5 Stereochemistry
Chapter 5 Stereochemistry References: 1. Title: Organic Chemistry (fifth edition) Author: Paula Yurkanis Bruice Publisher: Pearson International Edition 2. Title: Stereokimia Author: Poh Bo Long Publisher:
More informationChapter 5 Stereochemistry
Organic Chemistry, Second Edition Janice Gorzynski Smith University of Hawai i Chapter 5 Stereochemistry Prepared by Rabi Ann Musah State University of New York at Albany Copyright The McGraw-Hill Companies,
More informationLesson 4. Molecular Geometry and Isomers II. Lesson 4 CH 3 HO H OH
Lesson 4 Molecular Geometry and Isomers II 4 Lesson 4 3 O O 3 Organic Edge A. Structural Isomers (onstitutional Isomers) 1. Structural isomers are molecules that share the same molecular formula but differ
More informationOrganic Chemistry Chapter 5 Stereoisomers H. D. Roth
Organic Chemistry Chapter 5 Stereoisomers. D. Roth 11. Chirality of conformationally mobile systems ring compounds Monosubstituted cycloalkanes cannot have an asymmetric carbon in the ring, because there
More informationStereochemistry CHAPTER SUMMARY
2 7 2 7. Introduction APTER SUMMARY Isomers are compounds with identical molecular formulas but different structural formulas. Structural or constitutional isomers differ in the bonding arrangement of
More informationChapter 5 Stereochemistry. Stereoisomers
Chapter 5 Stereochemistry Stereoisomers Same bonding sequence Different arrangement in space Example: OOC-C=C-COO has two geometric (cis-trans) isomers: COO COO COO COO Stereochemistry Slide 5-2 1 Chirality
More informationStereochemistry. Based on McMurry s Organic Chemistry, 6 th edition
Stereochemistry Based on McMurry s Organic Chemistry, 6 th edition Stereochemistry! Some objects are not the same as their mirror images (technically, they have no plane of symmetry)! A right-hand glove
More information9. Stereochemistry. Stereochemistry
9. Stereochemistry Stereochemistry Some objects are not the same as their mirror images (technically, they have no plane of symmetry) A right-hand glove is different than a left-hand glove (See Figure
More informationChapter 6. Isomers and Stereochemistry
Chapter 6. Isomers and Stereochemistry Learning objectives: 1. Differentiate chiral and achiral molecules. 2. Recognize and draw structural isomers (constitutional isomers), stereoisomers including enantiomers
More informationStereochemistry. 3-dimensional Aspects of Tetrahedral Atoms
Stereochemistry 3-dimensional Aspects of Tetrahedral Atoms Chiral Entire molecules or simply atoms that do not possess a plane of symmetry are called chiral. Conversely, the term achiral is applied to
More information(2/94)(6,7,9/95)(8,9/97)(12/99)(1/00) Neuman Chapter 4
4: Stereochemistry Tetrahedral Carbon Configurations Stereoisomers and R,S Assignments The Number and Types of Stereoisomers Drawing Structures of Stereoisomers Cyclic Molecules Optical Activity Preview
More informationC 4 H 10 O. butanol. diethyl ether. different carbon skeleton different functional group different position of FG
hapter 5: Stereoisomerism- three-dimensional arrangement of atoms (groups) in space 5. verview of Isomerism Isomers: different chemical compounds with the same formula onstitutional isomers: same formula,
More informationChem 341 Jasperse Ch. 9 Handouts 1
Chem 341 Jasperse Ch. 9 andouts 1 Ch. 9 Stereochemistry Stereoisomers have the same condensed formulas and basic bonding sequence, but have different 3-dimensional shape and cannot be interconverted 9.1,2
More informationOrganic Chemistry. M. R. Naimi-Jamal. Faculty of Chemistry Iran University of Science & Technology
Organic Chemistry M. R. Naimi-Jamal Faculty of Chemistry Iran University of Science & Technology Chapter 6. Stereochemistry Based on McMurry s Organic Chemistry, 6 th edition Stereochemistry Some objects
More informationOrganic Chemistry. Chemical Bonding and Structure (2)
For updated version, please click on http://ocw.ump.edu.my Organic Chemistry Chemical Bonding and Structure (2) by Dr. Seema Zareen & Dr. Izan Izwan Misnon Faculty of Industrial Science & Technology seema@ump.edu.my
More informationSTEREOGENIC CENTER (Chiral Center,Asymmetric Center) Atom (usually carbon) to which 4 different groups are attached: W Z C X Y
STEREOGENI ENTER (hiral enter,asymmetric enter) Atom (usually carbon) to which 4 different groups are attached: W Z X Y Many, but not all, molecules which contain a stereogenic center are chiral. (A molecule
More informationSTEREOGENIC CENTER (Chiral Center,Asymmetric Center)
STEREOGENI ENTER (hiral enter,asymmetric enter) Atom (usually carbon) to which 4 different groups are attached: W Z X Y Many, but not all, molecules which contain a stereogenic center are chiral. (A molecule
More information10/4/2010. Sequence Rules for Specifying Configuration. Sequence Rules for Specifying Configuration. 5.5 Sequence Rules for Specifying.
5.5 Sequence Rules for Specifying Configuration Configuration The three-dimensional arrangement of substituents at a chirality center Sequence rules to specify the configuration of a chirality center:
More informationgeometric isomers (diastereomers)
Symmetry Monarch butterfly: bilateral symmetry= mirror symmetry Whenever winds blow butterflies find a new place on the willow tree -Basho (~6-69) 5 hapter 7: Stereochemistry - three-dimensional arrangement
More informationDue Date: 2) What is the relationship between the following compounds?
Assignment #5 Name CHEM201 Student #: Due Date: MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) What type of isomers are CH3CH2OCH3 and CH3CH2CH2OH?
More informationChapter 4: Stereochemistry
Chapter 4: Stereochemistry Introduction To Stereochemistry Consider two of the compounds we produced while finding all the isomers of C 7 16 : C 3 C 3 2-methylhexane 3-methylhexane C 2-methylhexane Bu
More informationChapter 6. Isomers and Stereochemistry
hapter 6. Isomers and Stereochemistry Learning objectives: 1. Differentiate chiral and achiral molecules. 2. Recognize and draw structural isomers (constitutional isomers), stereoisomers including enantiomers
More informationCopyright 2009 James K Whitesell
Copyright 2009 James K Whitesell 5-1 These two molecules, cyclopropylcyclopentane and cyclobutycyclobutane have the same number of carbon and hydrogen atoms and thus they are constitutional isomers. 5-2
More informationORGANIC - BROWN 8E CH.3 - STEREOISOMERISM AND CHIRALITY.
!! www.clutchprep.com CONCEPT: TYPES OF ISOMERS Isomers are used to describe relationships between similar molecules. We can order these relationships in order of increasing similarity Page 2 CONCEPT:
More information9. Stereochemistry: Introduction to Using Molecular Models
9. Stereochemistry: Introduction to Using Molecular Models The first part of this document reviews some of the most important stereochemistry topics covered in lecture. Following the introduction, a number
More information(1) Check to see if the two compounds are identical. (2) Recall the definitions of stereoisomers, conformational isomers, and constitutional isomers.
MCAT Organic Chemistry Problem Drill 04: Stereochemistry Question No. 1 of 10 Question 1. Determine the relationship of the molecules shown: O O Question #01 (A) Identical (B) Constitutional isomers (C)
More informationSTEREOISOMERS ARRANGEMENTS IN 3D- SPACE
STEREOISOMERS ARRANGEMENTS IN 3D- SPACE 1 Isomers 2 Physiological Proper@es of Stereoisomers (Enan@omers) Enan@omers can have very different physiological proper@es. 3 Oranges and Lemons found in oranges
More informationSTEREOCHEMISTRY A STUDENT SHOULD BE ABLE TO:
A STUDENT SHOULD BE ABLE TO: STEREOCHEMISTRY 1. Determine the relationship between two given structures (which may be any of the kinds below). Also, define the following terms, and give examples of pairs
More informationCHEM 263 Oct 18, Do they have the same molecular formula?
EM 263 ct 8, 206 To compare the relationship of 2 structures: Do they have the same molecular formula? o ot isomers Do they have the same sequence of atoms (i.e. connectivity)? o onstitutional or tructural
More informationCSUS - CH6B Fischer projection and R/S configurations Instructor: J.T., P: 1. a) Fischer Projection can be rotated by 180 only!
CSUS - C6B Fischer projection and R/S configurations Instructor: J.T., P: () Fischer Projection: orizontal line is coming out of the plane of the page. Vertical line is going back behind of the plane of
More informationStereochemistry Terminology
Stereochemistry Terminology Axis of symmetry: When an operation on an axis C n, where n = 360 /rotation, leads to a structure indistinguishable from the original. C 2 180 Plane of symmetry: (σ) A plane
More informationLecture Topics: I. Stereochemistry Stereochemistry is the study of the three dimensional structure of molecules
Stereochemistry eading: Wade chapter 5, sections 5-- 5-7 Study Problems: 5-26, 5-3, 5-32, 5-33, 5-34 Key oncepts and Skills: assify molecules as chiral or achiral, and identify planes of symmetry. Identify
More informationSTEREOCHEMISTRY. 2. Define the following, and tell whether or not a given compound or structure fits the description or possesses the feature.
A STUDENT SOULD BE ABLE TO: STEREOEMISTRY 1. Determine the relationship between two given structures (which may be any of the kinds below). Also, define each of the following terms, and give examples of
More informationChapter 6 Principles of Stereochemistry
6.1 (a) This compound is chiral. Methane is achiral. Instructor Supplemental Solutions to Problems 2010 Roberts and Company Publishers Chapter 6 Principles of Stereochemistry Solutions to In-Text Problems
More informationa. Does the model have a plane of symmetry? Yes No The central carbon is said to be a stereocenter, stereogenic center, or chiral carbon.
Name: TA Name Lab Section: Day Time OPTICAL ISOMERISM 1. Construct a model that has a central carbon atom with 4 different colored spheres attached to it, representing four different atoms or groups. Draw
More information18 Isomerism and stereochemistry
s manual for Burrows et.al. hemistry Third edition 8 Isomerism and stereochemistry s to worked examples WE 8. Structural isomers (on p. 88 in hemistry ) For the following four compounds, A D, identify
More information(S)-(-)-Dopa, used to treat Parkinson's disease, and its medically ineffective (R)-(+) enantiomer
C h a p t e r F i v e: Stereoisomerism N 2 2 N (S)-(-)-Dopa, used to treat Parkinson's disease, and its medically ineffective (R)-(+) enantiomer CM 321: Summary of Important Concepts YConcepts for Chapter
More informationEnantiomers. nonsuperimposable mirror image Both Configuration will be opposite. Both Configuration will be opposite
Optical Isomerism Isomerism of Organic Molecules: Two chiral centers Many organic compounds have more than one asymmetric carbon. The more asymmetric carbons a compound has, the more number of stereoisomers
More informationBasic Stereochemical Considerations
Basic Stereochemical Considerations Key words: chirality, chiral carbon, enantiomers, diastereomers, absolute configuration, relative configuration, optical activity 1 Key Concepts Basics of projection
More informationExperiment 6. Stereochemistry
Experiment 6. Stereochemistry Introduction Organic molecules with the same molecular formula but different arrangements of atoms are called isomers. Structural isomers are different because the location
More informationSTEREOCHEMISTRY A STUDENT WHO HAS MASTERED THE MATERIAL IN THIS SECTION SHOULD BE ABLE TO:
STEREOEMISTRY A STUDENT WO AS MASTERED TE MATERIAL IN TIS SETION SOULD BE ABLE TO: 1. Determine the relationship between two given structures (which may be any of the kinds below). Also, define each of
More informationStereochemistry Terminology for two pure isomeric compounds, both of which are chiral? A pair of stereoisomers
Name Last, irst STEECEMISTY This handout will help you understand stereoisomerism, naming conventions and relationships between stereoisomers. I hope that you will use this to help you study for exam 1.
More informationLecture 8: September 13, 2012
CHM 223 Organic Chemistry I Fall 2012, Des Plaines Prof. Chad Landrie Lecture 8: September 13, 2012 Skillbuilder 2 Ch. 5: Stereochemistry (Sec8ons 5.1-5.5) CHM 223 Organic Chemistry I Fall 2012, Des Plaines
More information1. Make two superimposable models of bromochloroiodomethane. Position your models on your desk to prove that they are superimposable.
HM 204 Organic hemistry Introduction to Stereochemistry Recall that two models are identical if they can be superimposed without breaking bonds. Recall that conformations (conformers) are structures that
More informationIN-CLASS PROBLEM. ChemistryOnline, STEREOCHEMISTRY OF TETRAHEDRAL CENTERS. ChemistryOnline, No Plane of Symmetry
hapter 5 Draw the structure of bromocyclopentane. Stereochemistry Reproduction or distribution of any of the content, or any of the images in this presentation is strictly prohibited without the expressed
More informationMOLECULAR MODELS : STEREOISOMERS
MM.1 MOLEULAR MODELS : STEREOISOMERS Note: No pre-laboratory summary is required for this experiment, but there are some topics you most probably need to review from 351 and you may want to start work
More informationStereochemistry Structural or constitutional isomers... have the same molecular formula but different connectivity (skeletal, positional, functional)
Stereochemistry Structural or constitutional isomers... have the same molecular formula but different connectivity (skeletal, positional, functional) Stereoisomers... have the same connectivity but a different
More informationFor more info visit
Bond Fission: a) Homolytic fission: Each atom separates with one electron, leading to the formation of highly reactive entities called radicals, owing their reactivity to their unpaired electron. b) Heterolytic
More informationTwo enantiomers of a racemic carboxylic acid (to be separated)
7.8 FISCER PRJECTINS 237 (R)-RC 2 (S)-RC 2 Two enantiomers of a racemic carboxylic acid (to be separated) Figure 7.5 RESLUTIN F A RACEMIC CARBYLIC ACID. (S)-RN 2 ne enantiomer of a chiral amine + (R)-RC
More informationCHEM 261 Feb. 2, Stereochemistry and Chirality
70 EM 261 eb. 2, 2017 Stereochemistry and hirality hiral object or molecule: has a non-superimposable mirror image Achiral object: not chiral, has a superimposable mirror image 1848 - Louis Pasteur separated
More informationNames. Chiral: A chiral object is not superimposable upon its mirror image. A chiral object contains the property of "handedness.
CEM 241 IN-CLASS #3 MOLECULAR MODELS EXERCISE Names Stereoisomerism Construct a model containing a tetrahedral carbon (black ball) that is attached to four different atoms (use the green, orange, purple
More informationAssigning Stereochemistry I What is stereochemistry?
S. Lievens, March 0 University of alifornia, Davis For use in UDavis hemistry 8/8 Series Assigning Stereochemistry I What is stereochemistry? Types of isomers As organic molecules get larger (more than
More informationFall Organic Chemistry Experiment #6 Fractional Crystallization (Resolution of Enantiomers)
Suggested Reading: Fall Organic Chemistry Experiment #6 Fractional Crystallization (Resolution of Enantiomers) Jones Section 4.9 Physical Properties of Diastereomers: Optical Resolution pages 176-178 Introduction
More informationCHEM J-10 June The structure of ( )-linalool, a commonly occurring natural product, is shown below.
CEM1102 2014-J-10 June 2014 The structure of ( )-linalool, a commonly occurring natural product, is shown below. 4 What is the molecular formula of ( )-linalool? C 10 18 O Which of the following best describes
More informationThree-Dimensional Structures of Drugs
Three-Dimensional Structures of Drugs Moore, T. (2016). Acids and Bases. Lecture presented at PHAR 422 Lecture in UIC College of Pharmacy, Chicago. Chiral drugs are sometimes sold as one enantiomer (pure
More informationExam Analysis: Organic Chemistry, Midterm 1
Exam Analysis: Organic Chemistry, Midterm 1 1) TEST BREAK DOWN: There are three independent topics covered in the first midterm, which are hybridization, structure and isomerism, and resonance. The test
More information02/07/2017. Isomerism. Structural isomerism. 1. Structural isomerism different linkages of atoms. Same molecular formula Different structural formulae
hain isomerism Position isomerism Metamerism Tautomerism Functional group isomerism Geometrical isomerism Optical isomerism 02/07/2017 Isomerism The presence of two or more compounds which has the same
More information4 1,2,3 - Clockwise 1,2,3 - Counterclockwise S
Assigning Stereochemistry using Fischer Projections: Fischer projections can be used to assign stereochemistry. If the th (lowest) priority group is vertical the other three groups will show clockwise
More informationCalculate a rate given a species concentration change.
Kinetics Define a rate for a given process. Change in concentration of a reagent with time. A rate is always positive, and is usually referred to with only magnitude (i.e. no sign) Reaction rates can be
More informationSTEREOCHEMISTRY AND STEREOELECTRONICS NOTES
- 1 - STEREOCHEMISTRY AND STEREOELECTRONICS NOTES Stereochemistry in Organic Molecules Conventions used in drawing molecules Also, Fischer projections can sometimes be useful for acyclic molecules with
More informationStereochemistry: Chiral Molecules. Constitutional Isomers - Review. Enantiomers and Chiral Molecules. Mirror images = handedness
Isomerism: Constitutional Isomers and Stereoisomers Chapter 5 Constitutional Isomers = same molecular formula, different connectedness Stereoisomers = same molecular formula, same connectivity of atoms
More informationSolutions 80 CHAPTER a) trans b) not stereoisomeric c) trans d) trans e) trans f) not stereoisomeric g) cis
80 CAPTE 5 killbuilder 5.9 Assigning configuration from a Fischer projection AIG TE CFIGUATI F TE CIALITY CETE I TE FLLWIG CMPUD C 2 olutions 5.1. trans not stereoisomeric trans trans trans f) not stereoisomeric
More informationChapter 5 Stereoisomerism
Chapter 5 tereoisomerism eview of Concepts Fill in the blanks below. To verify that your answers are correct, look in your textbook at the end of Chapter 5. Each of the sentences below appears verbatim
More informationExam 2 Chem 109a Fall 2004
Exam 2 Chem 109a Fall 2004 Please put your name and perm number on both the exam and the scantron sheet. Next, answer the following 34 multiple-choice questions on the scantron sheet. Then choose one A-type
More informationLecture 4: 12.4 Isomerism
Lecture 4: 12.4 Isomerism Learning Outcomes: At the end of the lesson the students should be able to : Define isomerism. Explain constitutional isomerism. chain isomers positional isomers functional group
More informationChapter 5: Stereoisomerism
hapter 5: Stereoisomerism [Sections: 5.1-5.9] 1. dentifying Types of somers Same MolecularFormula? A B compounds are not isomers Same onnectivity? D E constitutional isomers have different names (parent
More informationChapter 3: Stereochemistry & Chirality
Chapter 3: Stereochemistry & Chirality 1. Chiral & Achiral Compounds - Identifying Stereocenters 2. Assigning R & S configurations 3. Diastereomers - Molecules with two or more stereocenters 4. Properties
More information4Types of Isomers. 1. Structural Isomers/(Constitutional) 2. Geometric Isomers/(Cis/Trans) 3. Optical Isomers A. Enantiomers B.
4Types of Isomers 1. Structural Isomers/(Constitutional) 2. Geometric Isomers/(Cis/Trans) 3. Optical Isomers A. Enantiomers B. Diastereomers 4Types of Isomers C 4 10 C 4 10 O O O O O O O O O O O O C 3
More informationE30 ENANTIOMERS Chirality in organic chemistry
E30 ENANTIMERS hirality in organic chemistry TE TASK To investigate the nature of chirality in organic chemistry. TE SKILLS By the end of the experiment you should be able to: use molecular modelling kits
More informationGeneral Glossary. General Glossary
General Glossary Absolute configuration The actual three-dimensional structure of a chiral molecule. Absolute configurations are specified verbally by the Cahn-Ingold-Prelog R,S convention and are represented
More informationO N N. electrons in ring
ame I. ( points) Page 1 A. The compound shown below is a commonly prescribed antifungal drug. It belongs to a category of compounds known as triazoles. Analyze the geometry and other properties for various
More informationQuímica Orgânica I 2008/09. w3.ualg.pt\~abrigas QOI 0809 A3 1
Química Orgânica I 2008/09 w3.ualg.pt\~abrigas QOI 0809 A3 1 O O O 3 C 3 C O O O C 3 N O C 3 O O O O O O C 3 O w3.ualg.pt\~abrigas QOI 0809 A3 2 Adaptado de: Jo Blackburn; 2006, Prentice all; Organic Chemistry,
More informationLECTURE #09 Thurs., March 06, in Lect.07 s notes actually Biological relevance of chirality
EM 221 section 52 LETURE #09 Thurs., March 06, 2008 ASSIGNED READINGS: TDAY S LASS: 5.1-5.4 in Lect.07 s notes actually 5.21 Biological relevance of chirality 5.5-5.14 Drawing & naming enantiomers & diastereomers
More information1. Use appropriate curved arrows to indicate the complete mechanism of each of these reactions. KH (1 equiv.) + KCl THF. + HBr.
1. Use appropriate curved arrows to indicate the complete mechanism of each of these reactions. K (1 equiv.) TF K 3 2 2 3 enantiomer While writing the mechanism, justify both the regiochemistry the relative
More informationOrganic Chemistry. Stereochemistry
Organic Chemistry by Nurlin Abu Samah, Dr. Md. Shaheen & Dr. Nadeem Akhtar Faculty of Industrial Sciences & Technology nurlin@ump.edu.my Chapter Description Aims The students should understand the fundamental
More informationCHEM 241 CHIRALITY CHAP 4 ASSIGN
EM 241 IRALITY AP 4 ASSIGN 1. Assume that a particular reaction gives the following two enantiomers as products in the following ratio. What is the enantiomeric excess (% ee) associated with this reaction?
More informationCHAPTER 26 STEREOISOMERISM SOLUTIONS TO REVIEW QUESTIONS. ƒ C Cl ƒ
EINS26-400-417.v1.qxd 11/9/07 1:13 PM Page 400 APTER 26 STEREOISOMERISM SOLUTIONS TO REVIEW QUESTIONS 1. A chiral carbon atom is one to which four different atoms or groups are attached and is a center
More informationOnce familiar with chiral centers, models, drawings and mental images NOW: Final representation of chiral centers: Fischer Projections
Once familiar with chiral centers, models, drawings and mental images NOW: Final representation of chiral centers: Fischer Projections Fischer Projections are 2-dimensional representations of 3-dimensional
More information1. (3 pts) Circle the highest priority substituent of the following list:
Ch 334 Midterm #3 November 17, 2006 Code 1. (3 pts) Circle the highest priority substituent of the following list: 2. (4 pts) Rank the following groups in order of increasing priority. Place the letter
More informationEssentials of Chapter 6
Essentials of Chapter 6 (Videos: conformational Analysis, Conformational Analysis of Cycloalkanes, Chirality, /S Nomenclature [Basic Advanced], ptical Activity) A. Stereochemical Structures Wedge Bond
More informationExperiment 8 Optical Isomers. In this experiment you will be given the opportunity to see the 3-dimensional aspects of
Experiment 8 Optical Isomers In this experiment you will be given the opportunity to see the 3-dimensional aspects of stereochemistry and optical isomers. Previously in class you were exposed to the concept
More informationCHEMISTRY PAPER No. : 7 MODULE No. : 23 (Optical Isomerism)
Subject Chemistry Paper No and Title Module No and Title Module Tag Paper 7 : Inorganic Chemistry-II (Metal-Ligand Bonding, Electronic Spectra and Magnetic Properties of Transition Metal Complexes) 23
More informationcomes forward STEREOISOMERS ISOMERS THAT ARE DIFFERENT BECAUSE OF THEIR ORIENTATION IN SPACE
STEREOCEMISTRY SOME DEFINITIONS WIT EXAMPLES PRESENTING STEREO STRUCTURES CIRAL CENTER REPRESENTAITON goes back goes back in the plane of the paper comes forward comes forward DOTTED LINE - WEDGE goes
More informationSECOND YEAR ORGANIC CHEMISTRY - REVISION COURSE Lecture 1 MOLECULAR STRUCTURE 1: STEREOCHEMISTRY & CONFORMATIONAL ANALYSIS
Prof Ben Davis SECND YEAR RGANIC CEMISTRY - REVISIN CURSE Lecture 1 MLECULAR STRUCTURE 1: STERECEMISTRY & CNFRMATINAL ANALYSIS Good books and reading: Carey and Sundberg, Part A, Ch 2 & 3 Stereochemistry
More informationCHEMpossible. 261 Exam 1 Review
CHEMpossible 261 Exam 1 Review A. Rank the following carboxylic acids from least acidic to most acidic: B. Draw the line-angle formulas for three acylic (non-cyclic) esters with the molecular formula C
More information10/4/2010. Chapter 5 Stereochemistry at Tetrahedral Centers. Handedness. 5.1 Enantiomers and the Tetrahedral Carbon
John E. McMurry http://www.cengage.com/chemistry/mcmurry Chapter 5 Stereochemistry at Tetrahedral Centers Richard Morrison University of Georgia, Athens Handedness Right and left hands are not identical
More informationOption II: Chiral + Achiral = Optically Active Diastereomers
Option II: Chiral + Achiral = Optically Active Diastereomers What about additions to chiral alkenes? The previous examples were reactions done on achiral alkenes. What is the difference when an alkene
More informationLearning Guide for Chapter 17 - Dienes
Learning Guide for Chapter 17 - Dienes I. Isolated, conjugated, and cumulated dienes II. Reactions involving allylic cations or radicals III. Diels-Alder Reactions IV. Aromaticity I. Isolated, Conjugated,
More informationCHEM 261 Feb. 2, Pheromone: from Greek pherein horman meaning to carry excitement. Only about 50 % of the population can smell this compound
70 EM 61 eb., 017 Pheromone: from Greek pherein horman meaning to carry excitement O Only about 50 % of the population can smell this compound omenclature of Alkynes Rules: - ind longest chain with max
More informationGOODLUCK TUITION CENTER FOR CHEMISTRY. 655 A 48TH STREET 9 TH SECTOR CHENNAI - 78 Ph: Cell : ISOMERISM
GOODLUCK TUITION CENTER FOR CHEMISTRY 655 A 48TH STREET 9 TH SECTOR CHENNAI - 78 Ph: 2366 3848 Cell : 9444357037 ISOMERISM 1. Mesotartaric acid is an optically inactive compound with asymmetric carbon
More informationStereochemistry & Polarimetry notes
Reminder: These notes are meant to supplement, not replace, the laboratory manual. Stereochemistry & Polarimetry notes History Application: Approximately 25% of all drugs are marketed as either racemates
More informationName. Optical Isomers
Name KEY Lab Day Optical Isomers Introduction: Stereoisomers are compounds that have the same structural formulas, but differ in their spatial arrangements. Two major types of stereoisomers are geometric
More information= ( 3 ) + 2 ( 3 ) = ( ) = = ( ) = 20 H H
Columbia University 92CORG12.DOC CEM S3443D Summer 1992 Professor Grace B. Borowitz Exam No. 2 June 17, 1992 Name: Grade: Please use a non-red pen. Answer questions in the provided space. If you write
More informationTopic 5 Stereochemistry and optical isomers Isomerism
Topic 5 Stereochemistry and optical isomers Isomerism Recap lassification of isomers same molecular formula onstitutional Different nature/sequence of bonds Stereoisomers Different arrangement of groups
More informationStereochemistry. Conformers: Compounds that differ by orientation of atoms in space. They are interconvertible via rotation about single bonds.
Stereochemistry Terms onformers: ompounds that differ by orientation of atoms in space. They are interconvertible via rotation about single bonds. onstitutional isomers (also called structural isomers):
More information1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound?
CEM 331: Chapter 1/2: Structures (Atoms, Molecules, Bonding) 1. What are the respective hybridizations of the atoms numbered 1 to 4 in this compound? N C 2 C N C 2 C N 1 2 3 4 1: three sigma bonds and
More information