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Organic Chemistry

Organic Chemistry. Chapter 22. Vocabulary. Organic Chemistry Hydrocarbons Saturated Unsaturated Alkanes Alkenes Alkynes Cis-trans isomerism. Carbonyl group Ketones Aldehydes Carboxylic acids Carboxyl group Ester Ether Amine. Saturated vs. Unsaturated Hydrocarbons.

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Organic Chemistry

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  1. Organic Chemistry Chapter 22

  2. Vocabulary • Organic Chemistry • Hydrocarbons • Saturated • Unsaturated • Alkanes • Alkenes • Alkynes • Cis-trans isomerism • Carbonyl group • Ketones • Aldehydes • Carboxylic acids • Carboxyl group • Ester • Ether • Amine

  3. Saturated vs. UnsaturatedHydrocarbons • Hydrocarbons are molecules composed of carbon & hydrogen • Each carbon atom forms 4 chemical bonds • A saturated hydrocarbonis one where all C - C bonds are “single” bonds & the molecule contains the maximum number of H-atoms • An unsaturated hydrocarbon is one where at least 1 C=C bond is double.

  4. Prefixes for # of Carbons

  5. Alkanes • Hydrocarbon chains where all the bonds between carbons are SINGLE bonds • Name uses the ending –ane • Examples: Methane, Propane, Butane, Octane • Formula: (CnH2n+2)

  6. Straight-Chain Alkanes • Straight-chain alkanes contain any number of carbon atoms, one after the other, in a chain pattern - meaning one linked to the next (not always straight) C-C-C C-C-C-C etc.

  7. Writing/drawing compounds Line formula

  8. Normal vs Branched Alkanes • NORMAL alkanes consist of continuous chains of carbon atoms • Alkanes that are NOT continuous chains of carbon atoms contain branches • The longest continuous chain of carbons is called the parent chain

  9. Endings • Attached carbon groups (substituents) end in –yl • Methyl CH3 - • EthylCH3CH2- • Propyl CH3CH2CH2 –   3-ethylpentane

  10. Names of branches • Carbon (alkyl) groups • Methyl CH3 - • EthylCH3CH2- • Propyl CH3CH2CH2 –

  11. Branched-Chain Alkanes • Rules for naming– 1. Longest C-C chain is parent 2. Number so branches have lowest # 3. Give position number to branch 4. Prefix (di, tri) more than one branch 5. Alphabetize branches (not prefix) 6. Use proper punctuation ( - and , )

  12. Designate the Location • Designate the location (number of the carbon on the parent chain) for each attached group 2-methyl 1 2 3 4 5

  13. Name this compound • 3,3-dimethylhexane

  14. Some Simple Alkanes • 2-methylpentane • 3-ethylhexane • 2,2-dimethylbutane • 2,3-dimethylbutane

  15. Branched-Chain Alkanes • From the name, draw the structure, in a right-to-left manner: 1. Find the parent, with the -ane 2. Number carbons on parent 3. Identify substituent groups (give lowest number); attach 4. Add remaining hydrogens

  16. 2 4 1 3 5 Example 1: 2,2-dimethylpentane • The parent chain is indicated by the ROOT of the name - “pentane”. This means there are 5 carbons in the parent chain. • “dimethyl” tells us that there are TWO methyl branches on the parent chain. A methyl branch is made of a single carbon atom. • “2,2-” tell us that BOTH methyl branches are on the second carbon atom in the parent chain.

  17. 2 4 1 3 5 6 7 Example 2: 3-ethyl-2,4-dimethylheptane • The parent chain is indicated by the ROOT of the name - “heptane”. This means there are 7 carbons in the parent chain. • “2,4-dimethyl” tells us there are TWO methyl branches on the parent chain, at carbons #2 and #4. • “3-ethyl-” tell us there is an ethyl branch (2-carbon branch) on carbon #3 of the parent chain.

  18. 3 5 4 6 2 7 1 8 5 3 2 4 6 7 1 8 Example 3: 2,3,3-trimethyl-4-propyloctane • The parent chain is indicated by the ROOT of the name - “octane”. This means there are 8 carbons in the parent chain. • “2,3,3-trimethyl” tells us there are THREE methyl branches - one on carbon #2 and two on carbon #3. • “4-propyl-” tell us there is a propyl branch (3-carbon branch) on carbon #4 of the parent chain.

  19. 4 3 5 5-ethyl- 3,4-dimethyl octane Example 4: Name the molecules shown! • parent chain has 5 carbons - “pentane” • two methyl branches - start counting from the right - #2 and #3 • 2,3-dimethylpentane • parent chain has 8 carbons - “octane” • two methyl branches - start counting from the left - #3 and #4 • one ethyl branch - #5 • name branches alphabetically

  20. Draw 2,2,4-trimethylpentane

  21. Structural Isomerism • Structural isomers are molecules with the same chemical formulas but different molecular structures n-pentane, C5H12 2-methlbutane, C5H12

  22. However, carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane.

  23. Your Turn • Draw all possible structural isomers of C5H12

  24. Practice

  25. IUPAC Rules for Naming Branched Alkanes • Find and name the parent chain in the hydrocarbon - this forms the root of the hydrocarbon name • Number the carbon atoms in the parent chain starting at the end closest to the branching • Name alkane branches by dropping the “ane” from the names and adding “yl”. A one-carbon branch is called “methyl”, a two-carbon branch is “ethyl”, etc… • When there are more than one type of branch (ethyl and methyl, for example), they are named alphabetically • Finally, use prefixes to indicate multiple branches

  26. CLASSWORK ASSIGNMENT • Review section 22-1 • make notes on NONMENCLATURE OF ALKANES and CYCLIC ALKANES • Pay attention to sample exercises!

  27. Alkenes are hydrocarbons that contain at least one carbon-carbon double bond Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond The suffix for the parent chains are changed from “ane” to “ene” and “yne” e.g. ethene, propyne the BONDS are numbered like branches so that the location of the multiple bond may be indicated Alkenes & Alkynes

  28. Alkenes & Alkynes: Examples ethene ethyne propene propyne butene 2-pentyne

  29. Aromatic Hydrocarbons Cycloalkanes • A cycloalkane is made of a hydrocarbon chain that has been joined to make a “ring”. • Note that two hydrogen atoms were lost in forming the ring!

  30. Aromatic Hydrocarbons Cycloalkanes • The two ends of the carbon chain are attached in a ring in a cyclic hydrocarbon • named as “cyclo- ____”

  31. Aromatic Compounds and Benzene Aromatic compounds contain benzene. Benzene, C6H6 , is represented as a six carbon ring with 3 double bonds. Two possible resonance structures can be drawn to show benzene in this form.

  32. Aromatic Hydrocarbons • Benzene derivatives can have two or more substituents: • 1,2-dimethylbenzene • 1,3-dimethylbenzene • 1,4-dimethylbenzene • Can use ortho for 1,2; meta for 1,3; and para for 1,4 (page 711) C C C C

  33. Isomers With organic compounds

  34. Isomers • There is a lack of rotation around a carbon to carbon multiple bond • Two possible arrangements: 1.trans configuration - substituted groups on opposite sides of double bond 2.cisconfiguration - same side

  35. Geometric Isomers Substituted groups are on opposite sides of the double bond (in this case, one is above, the other is below) Trans-2-butene Substituted groups are on the same side of the double bond (in this case, both are above) Cis-2-butene

  36. Cis-Trans Isomers - Examples cis-1,3-dimethylcyclobutane cis-1,2-dichlorocyclohexane trans-1-ethyl-2-methylcyclopropane

  37. Reactions With organic compounds

  38. Alkanes 1. Combustion reactions 2C2H6(g) + 7O2(g) 4CO2(g) + 6H2O(g) 2. Substitutionreactions CH4 + Cl2 CH3Cl + HCl Methane chloromethane 3. Dehydrogenationreactions CH3CH3CH2=CH2 + H2 Ethane ethene hv 500C

  39. Alkenes & Alkynes 1. Addition reactions a. Hydrogenation CH2 =CHCH3+ H2 CH3CH2CH3 Propene Propane b. Halogenation CH2 =CHCH2CH2CH3 + Br2 CH2 BrCHBrCH2CH2CH3 Pentene 1,2-dibromopentene c. Polymerization Small molecules = large molecules Catalyst

  40. Aromatic 1. Substitution reactions + Cl2  + HCl Catalyst = FeCl3

  41. Functional Groups With organic compounds

  42. Functional Groups • Functional group: an atom or group of atoms within a molecule

  43. Functional Groups

  44. Alcohols • contain an -OH (hydroxyl) group

  45. Halides & Carboxylic Acids • contain an -X (Halogen) group • F, Cl, Br, I, At • contain a carboxyl (-COOH) group

  46. Aldehydes and Ketones • contain a carbonyl (C=O) group

  47. : : : C H N H C H N H C H N C H 3 3 3 3 H C H C H 3 3 Methylamine Dimethylamine Trimethylamine (a 1° amine) (a 2° amine) (a 3° amine) Amines • contain an amino group; nitrogen bonded to one, two, or three carbon atoms • an amine may by 1°, 2°, or 3°

  48. Esters & Ethers • Ester: trapped carboxylic acid • Ether: Trapped oxygen

  49. Branches

  50. Functional Group -OH General Formula Name alkanone alkanol butan-2-one ethanol Examples ROH saturated ring CnH2n cycloalkane cyclohexane -COOH RCOOH alkanoic acid ethanoic acid (-CHO) -X -RX RCHO haloalkane alkanal ethanal chloroethane -COOR’ RCOOR’ ester methyl ethanoate R-O-R’ ethoxyethane ether amine -NH2 RNH2 methylamine

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