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Organic Chemistry. What is it? Study of compounds involving carbon –Carbon has the ability to make chains and rings with itself –Thousands of compounds.

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Presentation on theme: "Organic Chemistry. What is it? Study of compounds involving carbon –Carbon has the ability to make chains and rings with itself –Thousands of compounds."— Presentation transcript:

1 Organic Chemistry

2 What is it? Study of compounds involving carbon –Carbon has the ability to make chains and rings with itself –Thousands of compounds contain only Carbon and Hydrogen –Millions with other elements added Usually, Nitrogen, Oxygen, Sulfur, Halogens

3 Patterns Within the millions of compounds there are patterns that emerge –Carbon forms 4 Bonds –Hydrogen forms 1 Bond –Oxygen forms 2 Bonds –Halogens form 1 Bond

4 Identifying Compounds Name – Based on naming conventions (Usually IUPAC) Molecular Formula – Shows actual number of atoms present C 4 H 8 O 2 Empirical Formula – Shows the simplest whole number ratio of atoms C 2 H 4 O Structural Formula – Shows how the atoms are arranged CH 3 COCH 2 CH 2 OH

5 Cont. Graphical Formula – Shows how the atoms are arranged in space and bonded Similar to Lewis Structures but w/o the dots – CH 3 COCH 2 CH 2 OH

6 Cont. Skeletal Formula – Abbreviated form of graphical formula often omitting carbons and hydrogens CH 3 COCH 2 CH 2 OH

7 Example – Draw the structural, graphical, and skeletal formula for C 3 H 8

8 Example – Draw the structural, graphical, and skeletal formula for C 5 H 8 O 2

9 Example – Draw the structural, graphical, and skeletal formula for C 4 H 6

10 Homework Organic Worksheet #1

11 Alkanes Straight chain organic compounds containing only C, H, and sometimes halogens All carbons are sp 3 hybridized General formula C n H 2n+2 1 C = CH 4 6 C’s = C 6 H 14

12 Properties Nonpolar – Dissolve other nonpolar compounds –Hydrophobic – Water hating Good Lubricants and metal preservers C 1 to C 4 = (Gas) Fuels - Methane C 5 to C 8 = (Liq.) Fuels - Gasoline C 9 to C 16 = (Viscous Liq.) – Diesel Fuel C 17 and Up = (Very Viscous) - Greases

13 Cont.

14 Hydrocarbons and Saturation Hydrocarbons are compounds that only contain Carbon and Hydrogen Alkanes are saturated hydrocarbons –Carbons are saturated with hydrogen Compounds with double or triple bonds are unsaturated (more later)

15 Alkane Nomenclature Alkanes are named according to the longest carbon chain. (per IUPAC rules) System of prefixes to determine the number of carbons that are present. 1 = meth, 2 = eth, 3 = prop, 4 = but, 5 = pent 6 = hex, 7 = hept, 8 = oct, 9 = non, 10 = dec All alkanes end in -ane

16 Example – Draw the structural, graphical, and skeletal formula for ethane and butane

17 Example – Give the name and graphical formula for an alkane with 7 Carbons

18 Alkane Nomenclature Alkanes end in –ane Alkanes without branches are named according to the number of carbons Alkanes with branches are named according to longest chain of carbons The longest chain is numbered so that substituents receive the lowest number

19 Cont. When more than one of the same substituents is present use the prefixes di- tri-, tetra- If two or more substituents are present they are listed alphabetically (except prefix) Numbers are separated by commas, numbers and letters by hyphens

20 Substituent Groups Alkyl Groups – A hydrocarbon missing a hydrogen CH 3 – Methyl CH 3 CH 2 – Ethyl CH 3 CH 2 CH 2 – Propyl CH 3 CH 2 CH 2 CH 2 – Butyl Halogens Cl – ChloroBr – Bromo F – Fluoro I – Iodo

21 Name the alkane

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28 Other Alkyl Groups Isopropyl Sec-Butyl Isobutyl Tert-butyl

29 Name the alkane

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33 Isomers Same formula different compound Structural Isomers –Completely different bonding pattern Stereoisomers –Same bond pattern

34 Draw and name the isomers of C 4 H 10

35 Homework Organic Worksheet #2 Read pages 51-60

36 Dash Line Wedge Drawings A way of representing arragement in space Lines represent bonds in the plane Wedges come out of the plane and Dashed lines go into the plane Draw for Methane

37 Newman Projections Another way of showing arrangement in space. Look at the molecule for the end view Draw Newman Projection for Ethane

38 Alkane Confromations Alkanes are free to rotate because of single bond. Overlap of one orbital (sigma bond) Different arrangements are called rotamers. –A Stereoisomer Rotate to give minimum repulsion

39 Draw the most stable conformation of chloropropane

40 Cycloalkanes Alkanes that from ring structures Not necessarily a circle All carbons are still sp 3 hybridized Saturated compounds General Formula C n H 2n

41 Cycloalkane Nomenclature Named by placing cyclo- in front of the alkane name of the longest carbon ring If there is only one substituent there is no need to number it If there are multiple substituents the must be numbered. –Number by alphabetical order

42 Name the cycloalkane

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44 Draw cyclopentane and cyclohexane

45 Name the cycloalkane

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47 Draw 1-chloro-4-ethyl-2-methylcyclohexane

48 Conformations of Cycloalkanes Cycloalkanes take on interesting shapes Consider cyclopropane What must the bond angles be? 60 degrees! –Because 3 points determine a plane

49 Cont. Consider cyclobutane What are the bond angles? 88 degrees There is a slight “puckering” of the bonds

50 Cont. Consider cyclohexane What must the bond angles be? 109.5! Six membered rings are very common Takes on two puckered conformations Chair and boat conformations

51 Chair Conformation Named because it looks like a chair Most stable conformation

52 Boat Conformation Less stable because of repulsion

53 Configurational Isomers Same bond pattern different arrangement in space Called cis- and trans- isomers Cis- same side Trans- opposite Cis and trans molecules are different molecules Different boiling points Fig. 2.7 in book. (Page 60)

54 Draw the cis and trans forms of 2,3-dimethylcyclopropane

55 Homework Chapter 2 #’s 33,34,36,37ab,41 Organic Worksheet #3

56 Reactions of Alkanes Alkanes are fairly boring from a chemistry point of view. Meaning they are fairly unreactive Make very good solvents Two types of reactions –Burning –Reacting with halogens

57 Combustion When alkanes react with oxygen they can burn Complete combustion of alkanes yields carbon dioxide and water CH 4 + 2O 2  CO 2 + 2H 2 O + heat Incomplete combustion yeilds carbon monoxide and water

58 Halogenation Process of adding a halogen to an alkane Process must take place in the light General form R – H + X – X  R –X + H – X Where R is an alkane and X is a halogen Called a substitution reaction A hydrogen is substituted for a halogen When chlorine is added it is called chlorination and so on

59 Cont. Excess halogen allows the reaction to continue CH X 2  CX HX Reactions of straight chain alkanes gives a mixture of products C 3 H 8 + Cl 2  ?

60 Cycloalkanes Unsubstituted cycloalkanes give only one product when reacted with a halogen Write the balanced reaction when cyclobutane is reacted with bromine

61 Mechanism of Substitution The Mechanism is a process by which the reaction takes place Halogenation is a Free Radical Chain Reaction Made up of three steps –Initiation –Propagation –Termination

62 Initiation Beginning step Energy from light is required to break the halogen bond (Weaker than C-C or C-H) Creates a radical (Free atom)

63 Propagation Continuing the reaction Radicals react with the alkane and more halogens to create more radicals

64 Termination Ending the reaction Radicals react with radicals to stop the reaction

65 Problems 2.44


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