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Organic Chemistry

Organic Chemistry. Organic Chemistry. Organic Chemistry: The chemistry of carbon and carbon-based compounds. Organic Chemistry in everyday life: Smells & tastes: fruits, chocolate, fish, mint Medications: Aspirin, Tylenol, Decongestants, Sedatives

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Organic Chemistry

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  1. Organic Chemistry

  2. Organic Chemistry Organic Chemistry: The chemistry of carbon and carbon-based compounds Organic Chemistry in everyday life: Smells & tastes: fruits, chocolate, fish, mint Medications:Aspirin, Tylenol, Decongestants, Sedatives Addictive substances: Caffeine, Nicotine, Alcohol Hormones/Neurotransmitters: Adrenaline, Epinephrine Food/Nutrients: Carbohydrates, Protein, Fat, Vitamins Genetics: DNA, RNA Consumer products: Plastics, Nylon, Rayon, Polyester

  3. Organic Chemistry • Also the “weed-out” class for pre-med students! • Notoriously difficult college class.

  4. Question: • What makes a molecule an organic molecule? • The presence of carbon-hydrogen bonds!

  5. The simplest hydrocarbons: Alkanes • Compounds containing only C and H • All bonds are single bonds • Names end in -ane

  6. Expanded and Condensed Structures

  7. Structural Formulas • “Lazy” way to write the Hydrogens • Instead of drawing the bonds, just state how many hydrogens are attached • NOTE: The bonds are between CARBONS in a parent chain, and not hydrogens! Structural Formula Expanded Structural formula

  8. Names of Alkanes The names of alkanes • are determined by the IUPAC (International Union of Pure and Applied Chemistry) system. • end in –ane. • with 1-4 carbons in a chain use prefixes as follows. Name # Carbons Structural Formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3

  9. Prefixes for # of Carbons

  10. Learning Check A. Write the condensed formula for: H HHHH H C CCCC H H HHH H • What is its molecular formula? (Gives total # of each atom, does not indicate how they are arranged) C. What is its name? CH3─CH2─CH2─CH2─CH3 C5H12 pentane

  11. ALKANES (a “family” of hydrocarbons)   CnH2n+2 CH4 C2H6 C3H8 C4H10 etc. What would be the formula for decane, which has 10 carbons?

  12. Some Structures for Butane:All these structures mean the same thing!

  13. Cycloalkanes Cycloalkanes • are alkanes that form a loop. • have two hydrogen atoms fewer than the open chain. (remember each carbon has 4 bonds) • Formula will be CnH2n • are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms.

  14. Examples of Cycloalkanes Cyclopentane CH2 CH2 CH2 CH2 CH2 Cyclohexane CH2 CH2 CH2 CH2 CH2 CH2

  15. Some Properties of Alkanes Alkanes with 1-4 carbon atoms are: • methane, ethane, propane, and butane. • gases at room temperature. • used as heating fuels.

  16. Trivia question:Can you name a famous propane salesman?(He also sells propane-related accessories!)

  17. Trivia question:Can you name a famous propane salesman?

  18. Some Properties of Alkanes Alkanes with 5-8 carbon atoms are • liquids at room temperature. • pentane, hexane, heptane, and octane. • very volatile. • used to make gasoline. Alkanes with 9-17 carbon atoms • are liquids at room temperature • have higher boiling points. • are found in kerosene, diesel, and jet fuels.

  19. Combustion In combustion reactions, • alkanes react with oxygen. • CO2, H2O and energy are produced. Alkane + O2 CO2 + H2O + heat

  20. Learning Check Write a balanced equation for the complete combustion of propane.

  21. Isomers • Compounds with the same formula, but different structures

  22. Are these isomers?

  23. Structural isomers • same molecular formulas • different structural formulas

  24. Pentane C5H12 3 structural isomers • No other arrangements of C5H12 possible

  25. Chemists needed to expand the system of nomenclature to allow naming of individual structural isomers • Compounds without branches are called ‘straight chain’ alkanes • Branched compounds are named as derivatives of the longest straight chain in the molecule • The length of the longest chain provides the parent name • The straight chain is numbered to allow indication of the point of branching • The branches are named from the corresponding alkanes

  26. Naming the branches

  27. AlkaneAlkyl group Methane Methyl (CH3-) Ethane Ethyl (CH3CH2-) Propane Propyl (CH3CH2CH2-) Butane Butyl (CH3CH2CH2CH2-) Etc. 2-Methylbutane [Straight chain numbered so as to give the lower branch number]

  28. IUPAC rules for naming alkanes: • parentchain = longest continuous carbon chain  “alkane”. • branches on the parent chain are named as “alkyl” groups. • number the parent chain starting from the end that gives you the lower number for the first branch (principle of lower number). • assign numbers to the alkyl branches to show where they are in the parent chain • if an alkyl group appears more than once use prefixes: di, tri, tetra, penta…; each alkyl group must have a number! • 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) separating numbers from numbers with commas and letters from numbers with hyphens.

  29. Step 1. Find the parent chain. • Where is the longest continuous chain of carbons?

  30. Step 2. Number the parent chain. • Number the parent chain so that the attached groups are on the lowest numbers Methyl is on carbon #2 of the parent chain Methyl is on carbon #4 of the parent chain 1 2 3 4 5 GREEN is the right way for this one! 5 4 3 2 1 • 2 • 3 7 8 • 4 5 6 8 7 6 2 1 5 4 3 • 2 3 4 5 6 • 7 • 6 5 4 3 2 • 1 Groups on 2 and 5 Groups on 4, 6, and 7 Groups on 2, 3, and 5 Groups on 3 and 6

  31. Step 3. Designate where the group is attached to the parent chain. • Use the numbers of the parent chain from step 2 to designate the location of the attached groups to the parent chain. 2-methyl 1 2 3 4 5

  32. First, identify longest straight chain ‘…nonane’ Number so as to give lower numbers for branch points Branches at C3 and C6 Not at C4 and C7 6-ethyl,3,6-Dimethylnonane

  33. Identical substituents grouped together with a prefix • ‘di…’ for two identical • ‘tri…’ for three • ‘tetra…’ for four Substituents named in alphabetical order

  34. hexanes C6H14IUPAC names CH3 CH3CH2CH2CH2CH2CH3 CH3CHCH2CH2CH3 hexane 2-methylpentane CH3 CH3 CH3CH2CHCH2CH3 CH3CCH2CH3 CH3 3-methylpentane2,2-dimethylbutane CH3 CH3CHCHCH3 CH3 2,3-dimethylbutane

  35. Draw Some Simple Alkanes • 3-ethylhexane • 2,2-dimethylbutane • 2,3-dimethylbutane

  36. Alkanes • Now that we know how to name alkanes, let’s learn something about their chemical properties.

  37. Alkanes – chemical properties • The main chemical property of alkanes is that they have very low reactivity. • Why? Know these two reasons: 1. Ionic and polar compounds tend to be more reactive than non-polar compounds. Non-polar compounds don’t attract other molecules to react with. 2. C-C and C-H bonds are relatively strong. It takes a lot of energy to break them.

  38. Alkanes – chemical properties • The net effect is that alkanes have a fairly restricted set of reactions. You can: • burn them - destroying the whole molecule • react them with some of the halogens, breaking carbon-hydrogen bonds; • crack them, breaking carbon-carbon bonds.

  39. Cracking? • Cracking is the name given to breaking up large hydrocarbon molecules into smaller and more useful bits.

  40. Cracking • There isn't any single unique reaction happening in the cracker. The hydrocarbon molecules are broken up in a fairly random way to produce mixtures of smaller hydrocarbons, some of which have carbon-carbon double bonds. One possible reaction involving the might be:

  41. Alkanes – chemical properties • One chemical reaction that alkanes will readily undergo is combustion! • CH4 is methane – a main component of natural gas. Used to heat homes. • C2H4 (ethane) is also a main component of natural gas. • C3H8 (propane) – sold as fuel for camp stoves • C4H8 (butane) – used in lighters • C8H18 (octane) – major component of gasoline

  42. New topic: Functional Groups

  43. Functional Groups • As we’ve seen, alkanes don’t do much, except burn. • The chemistry of hydrocarbons is really controlled by what is attached to the alkanes. • Those attachments are called functional groups.

  44. Big Idea in Organic Chemistry Structure controls Function Each functional group has predictable reactivity

  45. Alkane Alcohol Carboxylic acid Alkene Ether Amine Alkyne Ketone Amide Haloalkane Aldehyde Amino acid Types of Organic Compounds Classified according to functional group

  46. Naming Alkenes & Alkynes Using the IUPAC alkane names: Alkene names change the end to -ene. Alkyne names change the end to -yne Ignore the names in parentheses – those are the old-fashioned names from before the naming rules!

  47. IUPAC Nomenclature for alkenes • Parent is longest chain containing the double bond. • -ane changes to -ene. • Number the chain so that the double bond has the lowest possible number. Chapter 7

  48. Naming Alkenes & Alkynes CH2= CH ─ CH2─ CH31-Butene CH3─ CH=CH─ CH32-Butene CH3 | CH3─ CH=C─CH32-Methyl-2-butene CH3─ CC ─ CH32-Butyne 1 3 2 4 2 1 3 4 4 2 1 3 1 3 2 4

  49. Naming Alkenes & Alkynes CH3─ CH2─ CC ─ CH3 2-Pentyne CH3 CH3─ CH2─ C=CH ─ CH3 3-Methyl-2-pentene CH2 – CH3 CH3─ CH2─ C=CH ─ CH3 3-Ethyl-2-pentene 1 3 5 2 4 1 3 5 2 4 3 1 5 2 4

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