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LOGO Spring 2014 Lecture 10: Organic Compounds Course lecturer : Jasmin Šutković 29 th April 2014.

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Presentation on theme: "LOGO Spring 2014 Lecture 10: Organic Compounds Course lecturer : Jasmin Šutković 29 th April 2014."— Presentation transcript:

1 LOGO Spring 2014 Lecture 10: Organic Compounds Course lecturer : Jasmin Šutković 29 th April 2014

2 Contents International University of Sarajevo 1.Functional classes and types of Org. Compounds Alkanes Alkenes Alkynes Aromatic compounds 2.Isomeric variations of Organic compounds 3.Reactivity of Organic compound 4.Chemical reactions of Organic Compounds Substitution Addition Elimination

3 Functional Groups and Classes of Organic Compounds  Organic compounds are covalent compounds composed primarily of carbon and hydrogen  Carbon is unique among the elements in its ability to catenate, forming long chains and cyclic structures in a wide variety of compounds  Functional groups are structural units that determine the chemical reactivity of a molecule under a given set of conditions – Can consist of a single atom or a group of atoms – Organic compounds are classified into several major categories based on the functional groups they contain

4 Organic Compounds main classes

5 Organic compounds functional groups

6 C n H 2n+2 CH 4 C 2 H 6 C 3 H 8 C 4 H 10 etc. C 2 H 6 ethane H H H—C—C—H H H Single bond… ALKANES

7 sp 3 conformation bond angles = 109.5 o σ-bonds (sigma) Rotation about C--C (conformations)

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10 Two isomers of butane C 4 H 10 : CH 3 CH 2 CH 2 CH 3 n-butane CH 3 CH 3 CHCH 3 isobutane Isomers are different compounds that have the same molecular formula

11 Alkanename CH 4 methane C 2 H 6 ethane C 3 H 8 propane C 4 H 10 butanes C 5 H 12 pentanes C 6 H 14 hexanes C 7 H 16 heptanes C 8 H 18 octanes C 9 H 20 nonanes C 10 H 22 decanes ……. C 20 H 42 eicosanes each new common name requires a new prefix…

12 hexanes C 6 H 14 common names CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 CH 3 CHCH 2 CH 2 CH 3 n-hexane isohexane

13 IUPAC nomenclature (Geneva, 1920) NAMES OF RADICALS (ALKYL GROUPS): CH 3 - “methyl”CH 3 Cl methyl chloride CH 3 OH methyl alcohol, etc. CH 3 CH 2 - “ethyl” CH 3 CH 2 CH 2 - “n-propyl”CH 3 CHCH 3 “isopropyl” |

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16 IUPAC rules for naming alkanes: 1.parent chain = longest continuous carbon chain  “alkane”. 2.branches on the parent chain are named as “alkyl” groups. 3.number the parent chain starting from the end that gives you the lower number for the first branch (principle of lower number). 4.assign “locants” to the alkyl branches. 5.if an alkyl group appears more than once use prefixes: di, tri, tetra, penta…; each alkyl group must have a locant! 6.the name is written as one word with the parent name last. The names and locants for the alkyl branches are put in alphabetic order (ignore all prefixes except iso) separating numbers from numbers with commas and letters from numbers with hyphens.

17 fossil fuels: natural gas petroleum coal petroleum is a complex mixture of hydrocarbons 1. solvents 2. fuels 3. raw materials for chemical syntheses separated into fractions by fractional distillation in an oil refinery

18 Alkenes C n H 2n “unsaturated” hydrocarbons C 2 H 4 ethylene Functional group = carbon-carbon double bond sp 2 hybridization => flat, 120 o bond angles σ bond & π bond => H 2 C=CH 2

19 C 3 H 6 propylene CH 3 CH=CH 2 C 4 H 8 butylenes CH 3 CH 2 CH=CH 2 α-butylene 1-butene CH 3 CH 3 CH=CHCH 3 CH 3 C=CH 2 β-butylene isobutylene 2-butene 2-methylpropene

20 There are two 2-butenes: cis-2-butene trans-2-butene “geometric isomers” (diastereomers)

21 E/Z system is now recommended by IUPAC for the designation of geometric isomerism. 1.Use the sequence rules to assign the higher priority * to the two groups attached to each vinyl carbon. 2. * * * * (Z)- “zusammen” (E)- “entgegen” together opposite CIS /TRANS or E-Z systems

22 Nomenclature of alkenes (basic steps): 1.Parent chain = longest continuous carbon chain that contains the C=C. 2.alkane => change –ane to –ene prefix a locant for the carbon-carbon double bond using the principle of lower number. 2.If a geometric isomer, use E/Z (or cis/trans) to indicate which isomer it is.

23 * * * * (Z)-3-methyl-2-pentene ( 3-methyl-cis-2-pentene ) (E)-1-bromo-1-chloropropene

24 Alkynes C n H 2n-2 C 2 H 2 H—C  C—H sp configuration Main representative is Acetylene OR Ethyne Example : C 3 H 4 CH 3 C  CH propyne OR methyl-acetylene

25 Nomenclature: common names: “alkylacetylene” IUPAC: parent chain = longest continuous carbon chain that contains the triple bond. add -yne prefix locant for the triple bond, etc. CH 3 CH 2 C  CCH 3 2-pentyne ethylmethylacetylene

26 “terminal” alkynes have the triple bond at the end of the chain: CH 3 CH 3 CH 2 C  CHHC  CCHCH 2 CH 3 1-butyne 3-methyl-1-pentyne ethylacetylene sec-butylacetylene

27 Aromatic compounds  Aromatic compounds are compounds which contain a benzene ring in their molecules  Benzene C 6 H 6  Methylbenzene C 7 H 8  Ethylbenzene C 8 H 10

28 Benzene The six carbon-carbon bonds in benzene are identical, intermediate in length between double and single bonds

29 Sigma bonding in benzene  Six carbon atoms joined to form a hexagonal planar ring.  Each carbon has four valence electrons!  One of these is used to form a bond with a hydrogen atom.  Two other electrons are used to form sigma bonds with the carbon atoms on either side.

30 Range and scope of aromatic chemistry  Pharmaceutical compounds, e.g. Morphine  Herbicides (Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants)  Detergents ( e.g. Sodium dodecylbenzenesulfonate- It is a major component of laundry detergent )  Dyes

31 Aromatic compounds and cancer  Some aromatic compounds are carcinogenic, e.g. Benzene  However, not all aromatic compounds are carcinogenic; aspirin is an example

32 1. First family is the hydrocarbons, which include alkanes, with the general molecular formula C n H 2n+2 where n is an integer; alkenes represented by C n H 2n ; alkynes represented by C n H 2n–2 ; and arenes (C n H n ) 2. Second family is the halogen-substituted alkanes, alkenes, and arenes, which include the alkyl halides and aryl halides Organic compounds groups :

33 3. Third family is the oxygen-containing organic compounds, which are divided into two main types: a.Those that contain at least one C–O single bond, which include alcohols, phenols, and ethers b.Those that contain a carbonyl group (> C  O), which include aldehydes, ketones, and carboxylic acids 4. Fourth family is the carboxylic acid derivatives; these are compounds in which the H atom on the –CO 2 H functional group is replaced either by an alkyl group, producing an ester, or by an amine, forming an amide 5. Fifth family is the nitrogen-containing organic compounds; these include amines, nitriles (which have a CN triple bond) and nitro compounds (which contain the NO 2 group)

34 Isomeric Variations in Structure Isomers are different compounds that have the same molecular formula Three main types of isomers: 1. Conformational 2. Constitutional (structural) 3. Stereoisomers

35 Conformational Isomers The C–C single bonds in alkanes are formed by the overlap of an sp 3 hybrid orbital on one carbon atom with an sp 3 hybrid orbital on another carbon atom, forming a  bond (sigma) Differences in three-dimensional structure resulting from rotation about a  bond are called differences in conformation, and each different arrangement is called a conformational isomer

36 Differences between the conformations are depicted in drawings called Newman projections – A Newman projection represents the view along a C–C bond axis, with the carbon that is in front shown as a point and the carbon that is bonded to it shown as a circle

37 – In one extreme, the eclipsed conformation, the C–H bonds on adjacent carbon atoms are parallel and lie in the same plane – In the other extreme, the staggered conformation, the hydrogen atoms are positioned as far from one another as possible

38 Conformational Isomers Newman projections are useful for predicting the stability of conformational isomers – The eclipsed conformation is higher in energy than the staggered conformation because of electrostatic repulsions between hydrogen atoms – The staggered conformation is the most stable because electrostatic repulsion between the hydrogen atoms on adjacent carbons is minimized

39 Newmans projections

40 Constitutional (Structural) Isomers Constitutional (structural) isomers differ in the connectivity of the atoms – The two alcohols, 1–propanol and 2–propanol, have the same molecular formula (C 3 H 8 O), but the position of the –OH group differs, which causes differences in their physical and chemical properties In the conversion of one constitutional isomer to another, at least one bond must be broken and reformed at a different position in the molecule

41 Propanol…

42 Stereoisomers Stereoisomers are molecules that have the same connectivity but whose component atoms have different orientations in space Two types of stereoisomers : 1. Geometric isomers differ in the relative placement of substituents in a rigid molecule; members of an isomeric pair are either cis or trans, with interconversion between the two forms requiring breaking and reforming one or more bonds; their structural differences causes them to have different physical and chemical properties and to exist as two distinct chemical compounds

43 Stereoisomers 2. Optical isomers are molecules that are mirror images but cannot be superimposed on one another in any orientation a.Optical isomers have identical physical properties, although their chemical properties may differ b.Molecules that are nonsuperimposable mirror images of each other are said to be chiral; an achiral object is one that can be superimposed on its mirror image

44 Stereoisomers

45 Most organic molecules that are chiral have at least one carbon atom that is bonded to four different groups – This carbon is designated by an asterisk in structural drawings and is called a chiral center, chiral carbon atom, asymmetric carbon atom, stereogenic center, or stereocenter A molecule and its non-superimposable mirror image are called enantiomers!

46 Stereoisomers

47 Interactions of enantiomers with other chiral molecules  In living organisms, every molecule with a stereocenter is found as a single enantiomer, not a mixture  At the molecular level, our bodies are chiral and interact differently with the individual enantiomers of a particular compound  Only one enantiomer of a chiral substance interacts with a particular receptor, initiating a response; the other enantiomer may not bind at all, or it may bind to another receptor, producing a different response

48 Cis and Trans conformations

49  The reactivity of a molecule is affected by the degree of substitution of the carbon bonded to a functional group; the carbon is designated as primary, secondary, or tertiary – Primary carbon is bonded to only one other carbon and a functional group – A secondary carbon is bonded to two other carbons and a functional group – A tertiary carbon is bonded to three other carbons and a functional group Reactivity of Organic Molecules

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51 Common Classes of Organic Reactions  Five common types of organic reactions: 1. Substitution 2. Elimination 3. Addition 4. Free-radical reactions 5. Oxidation-reduction reactions

52 Substitution  In a substitution reaction, one atom or group of atoms in a substance is replaced by another atom or group of atoms from another substance  A typical substitution reaction is the reaction of hydroxide ion with methyl chloride CH 3 Cl + OH –  CH 3 OH + Cl –  Methyl chloride has a polar C–Cl bond, so the carbon atom has a partial positive charge  Electronegative Cl atom is replaced by another electronegative species that is a stronger nucleophile, OH –

53 Elimination  Reactions in which adjacent atoms are removed, or “eliminated,” from a molecule with the formation of a multiple bond and a small molecule are called elimination reactions  General form:

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55 Addition  A reaction in which the components of a species A–B are added to adjacent atoms across a carbon-carbon multiple bond is called an addition reaction  An example is the reaction of HCl with ethylene to give chloroethane: HCl + CH 2  CH 2  CH 3 CH 2 Cl

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57 Free-Radical Reactions  Many important organic reactions involve free radicals, and the best known is the reaction of a saturated hydrocarbon with a halogen: CH 3 CH 3 + Br 2  CH 3 CH 2 Br + HBr Free radical reactions occur in three stages: initiation, propagation, and termination  At high temperature or in the presence of light, the weak Br–Br bond is broken in an initiation step that produces a number of Br atoms  During propagation, a bromine atom attacks ethane, producing a free radical, which then reacts with another bromine molecule to produce ethyl bromide; the sum of the propagation steps corresponds to the overall balanced equation for the reaction  Three possible termination steps: the combination of two bromine atoms, of two ethyl radicals, or of an ethyl and a bromine radical

58 HALOGEN ELEMENTS Are a group in the periodic table consisting of five chemically related elements, fluorine (F), chlorine(Cl), bromine (Br), iodine (I), and astatine (At). In the modern IUPAC nomenclature, this group is known as group 17 in PSE

59 Oxidation-Reduction Reactions  Oxidation-reduction reactions are common in organic chemistry and can be identified by changes in the number of oxygens at a particular position in the hydrocarbon skeleton or in the number of bonds between carbon and oxygen at that position

60 General Properties and Reactivity of Functional Groups  The functional groups characteristic of each class of organic compounds determine the general properties and reactivity of that class

61 Readings…  Follow the slides and the book chapter 24 named ORGANIC COMPOUNDS  http://www.chemguide.co.uk/basicorg/conv entions/names.html http://www.chemguide.co.uk/basicorg/conv entions/names.html This link is for additional tutorial for naming of simple organic compound… Two more lectures to go…


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