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Lesson 2 Isomerism
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Lesson 2 Isomerism

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  • 1. BIO-ORGANICCHEMISTRYLesson 2 INTRODUCTION Objectives: 1. Define isomerism. 2. Distinguish the different types of isomers present in carbon chains. 3. Draw structural formulas of various isomers. 4. Define chirality and optical activity. ust-nursing
  • 2. BIO-ORGANICCHEMISTRY ISOMERISMLesson 2 DEFINE ISOMERS INTRODUCTION Isomers refer to two or more molecules that have the same empirical formula but the individual atoms are connected in different ways, leading to different molecules. molecules ISOMERS Stereoisomers Constitutional Isomers Enantiomers Diastereomers (mirror-image) (non-mirror-image) Configurational cis - trans diastereomers diastereomers ust-nursing
  • 3. BIO-ORGANICCHEMISTRY ISOMERISMLesson 2 CONSTITUTIONAL ISOMER INTRODUCTION It has different connections among atoms. Skeletal – different carbon skeleton n- PENTANE ISOPENTANE Functional – different functional groups CH3CH2OH CH3OCH3 alcohol ether ust-nursing
  • 4. BIO-ORGANICCHEMISTRY ISOMERISMLesson 2 CONSTITUTIONAL ISOMER INTRODUCTION It has different connections among atoms. Positional- different position of functional groups NH2 H2 C C NH2 H3C H CH3 H3C C H2 ISOPROPYLAMINE PROPYLAMINE ust-nursing
  • 5. BIO-ORGANICCHEMISTRY ISOMERISMLesson 2 STEREOISOMERS INTRODUCTION It involves same connections among atoms but different geometry. Enantiomers- non-superimposable mirror – image. ust-nursing
  • 6. BIO-ORGANICCHEMISTRY ISOMERISMLesson 2 STEREOISOMER INTRODUCTION It has same connections among atoms but different geometry. Diastereomers- non-superimposable non-mirror – image. ust-nursing
  • 7. BIO-ORGANICCHEMISTRY ISOMERISMLesson 2 STEREOISOMERS INTRODUCTION It involves same connections among atoms but different geometry. Cis-trans: substituents on same side or opposite side of ring or double bond. http://www.uwplatt.edu/~sundin/354-7/l547-08.htm#CYCLO ust-nursing
  • 8. BIO-ORGANICCHEMISTRY CHIRALITY (ky-ral; Greek cheir; meaning “hand”)Lesson 2 It is when molecules are optically active… INTRODUCTION http://www.novactabio.com/biotrans.php Chiral image from Amino Acid Dating at http://www.creation-science-prophecy.com/amino/ ust-nursing
  • 9. BIO-ORGANICCHEMISTRY Chemistry connectionLesson 2 Chiral Drugs Just as various stereoisomeric forms of a chiral molecule have different physical INTRODUCTION properties, these stereoisomers manifests different biological properties. More dramatic examples of how a change in isomerisms can affect the biological properties of molecules are found in drugs . A more commonly prescribed medicine, Prozac where the racemic fluoxetine is extraordinarily effective as antidepressant but it has no activity against migraine. While the pure S- enantiomer however works remarkably well in preventing migrane. Drugs that come from natural sources, either directly or after chemical modification, are usually chiral and are generally found as a single enantiomer rather then the racemic mixture. Penicillin V, is an antibiotic isolated from Penicillium mold. This drug has a 2S, 5R, 6R configuration. To become biologically active, chiral molecules must fit into a chiral receptor at the target site, similar to hands fitting into gloves. Just as left hand can fit only into a left-hand glove, so as a particular stereoisomer can fit only into a receptor with proper complementary SOURCE: Adapted from Fundamentals shape. of Organic Chemistry by J. McMurry, 5th ed., 2003 (S)-Fluoxetine Penicillin V ust-nursing
  • 10. BIO-ORGANICCHEMISTRY Chemistry connectionLesson 2 Chiral Drugs Just as various stereoisomeric forms of a chiral molecule have different physical INTRODUCTION properties, these stereoisomers manifests different biological properties. More dramatic examples of how a change in isomerisms can affect the biological properties of molecules are found in drugs . A more commonly prescribed medicine, Prozac where the racemic fluoxetine is extraordinarily effective as antidepressant but it has no activity against migraine. While the pure S- enantiomer however works remarkably well in preventing migrane. Drugs that come from natural sources, either directly or after chemical modification, are usually chiral and are generally found as a single enantiomer rather then the racemic mixture. Penicillin V, is an antibiotic isolated from Penicillium mold. This drug has a 2S, 5R, 6R configuration. To become biologically active, chiral molecules must fit into a chiral receptor at the target site, similar to hands fitting into gloves. Just as left hand can fit only into a left-hand glove, so as a particular stereoisomer can fit only into a receptor with proper complementary SOURCE: Adapted from Fundamentals shape. of Organic Chemistry by J. McMurry, 5th ed., 2003 (S)-Fluoxetine Penicillin V ust-nursing

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