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Ch. 3 Review: Nomenclature: Organic Compounds

Ch. 3 Review: Nomenclature: Organic Compounds. Compounds of carbon--organic chemistry If they have only C and H, hydrocarbons e.g. alkanes: methane CH 4 , ethane C 2 H 6 , propane C 3 H 8 general formula: C n H 2n+2 Know Table 3.7 Functional Groups R = hydrocarbon group

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Ch. 3 Review: Nomenclature: Organic Compounds

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  1. Ch. 3 Review: Nomenclature: Organic Compounds • Compounds of carbon--organic chemistry • If they have only C and H, hydrocarbons • e.g. alkanes: methane CH4, ethane C2H6, propane C3H8 • general formula: CnH2n+2 • Know Table 3.7 • Functional Groups • R = hydrocarbon group • e.g. alcohols: methanol CH3OH, ethanol C2H5OH • e.g. amines: propyl amine, butylamine • Know functional groups in Table 3.8 Methanol (wood alcohol), CH3OH, is related to methane, CH4, by replacing one H with OH.

  2. Organic chemistry -- Chapter 20 • Introductory Topics Bonding & Structure -- Review Chapters 3, 9, and 10!! Types of Chemical Formulas e.g. 2-propanol (iso-propanol) or fully condensed structural formula expanded structural formula “line drawing” condensed structural formula (missing C’s and H’s are understood) !!! Always FOUR BONDS to Carbon !!!

  3. Isomerism • Isomers– different molecules with the same molecular formula Structural isomers--different pattern of atom attachment; different connectivity Stereoisomers—same atom attachments (connectivity), different spatial orientation Rotation about a single bond is not isomerism!!

  4. Structural Isomers • Structural Isomers-- same chemical formula, but different arrangement (connectivity) of atoms e.g. C3H8O - 3 isomers (2 alcohols, 1 ether) Number of possible isomers can be very large, e.g. 1-propanol 2-propanol ethyl methyl ether

  5. Stereoisomers • Stereoisomers—same atom attachments (connectivity), different spatial orientation • Optical isomers (enantiomers)—are molecules that are nonsuperimposable mirror images of each other • Geometric isomers—are stereoisomers that are not optical isomers, e.g. cis and trans

  6. Chiral Molecules • Are molecules that have nonsuperimposable mirror images • If 4 different groups are attached to carbon, it will be chiral • Chiral molecules will rotate plane-polarized light • Most physical properties are identical, but in a chiral environment enantiomers behave differently

  7. Isomerism; Overview

  8. Many Possible Compounds A Tremendous Variety of organic molecular structures and properties are possible, e.g.: poly(vinyl chloride) “PVC” vinyl chloride acetic acid aspirin

  9. More Organic Compounds methylamine Caffeine C8H10N4O2 fortunately, the subject is very systematic ! and is readily classified by “organic functional groups”

  10. Hydrocarbons • Alkanes CnH2n+2 CH4 methane C5H12 pentane C2H6 ethane C6H14 hexane C3H8 propane C7H16 heptane C4H10 butane C8H18 octane, etc…. alkyl groups: methyl CH3 ethyl CH3CH2 phenyl C6H5

  11. Alkane Nomenclature • Name parent chain--longest continuous chain • Number parent chain -- First branch gets lowest possible number • Name & number branches • Order branches -- Alphabetical order -- Multiple identical substituents get prefix Samples: CH3 CH3 CH3 CH3CH2CHCHCHCH2CHCH3 CH2CH3 5-ethyl-2,4,6-trimethyloctane 5-bromo-2-cyano-4-methylheptane (see book for detailed “rules” and other functional groups)

  12. Reactions of Alkanes (generally unreactive) • Combustion -- fuels! e.g. C5H12(l) + 8 O2(g) --> 5 CO2(g) + 6 H2O(l) • Free radical substitution (not selective!) C2H6(g) + Cl2(g) --> C2H5Cl(g) + HCl(g) • Dehydrogenation (reverse rxn is more common!) C2H6(g) --> H2C=CH2(g) + H2(g) • “Cracking” of hydrocarbons (petroleum industry) needs heat! needs heat and/or pressure! needs catalyst! needs heat!

  13. CH3 CH3 CH3CH2CHCH2CH=CCH3 Alkenes ~ C=C double bond CnH2n(with one double bond) • Geometric isomers are possible, e.g.: • Restricted C=C bond rotation • Trigonal planar geometry at C=C carbons • sp2 hybridization at C=C carbons • Nomenclature (C=C bond takes preference) cis-2-butene trans-2-butene cyclohexene 2,5-dimethyl-2-heptene

  14. Reactions of Alkenes addition to double bond RCH=CH2 + HX --> RXCH-CH3 + ≡ Markovnikov’s rule ~ “them that has, gets” (H goes on the C that already has the most H’s) Addition of non-polar reagents (H2, Br2, etc) also occurs

  15. Alkynes ~ C≡C Triple Bond CnH2n-2 (with one triple bond) • linear geometry at C≡C carbons • sp hybridization at C≡C carbons • no “cis-trans” isomers • similar addition reactions to alkenes (stepwise addition can occur) XY XY

  16. Aromatic Hydrocarbons (benzene and its derivatives) Benzene ~ C6H6 • planar 6-membered ring (especially stable) • all C-C distances equivalent • sp2 hydridization at all carbons • delocalized set of 3 double bonds (6 p electrons) other common aromatic hydrocarbons: napthalene anthracenes

  17. propylbenzene 4-phenyl-1-hexene 3 2 1 1-bromo-3-fluorobenzene Aromatic Nomenclature • Aromatic ring as substituent • Phenyl (C6H5–) • Benzyl (C6H5CH2–) • Monosubstituted benzene • (name of substituent)benzene • Some common “trivial” names • Toluene • Phenol • Polysubstituted benzene • Assign numbers to substituents

  18. Aromatic Substitution Rxns • Substitution Reactions of Aromatic Hydrocarbons (never addition!) X2 needs catalyst! X = Cl, Br X2 HNO3 (H+ catalyst) ( NOT aromatic! )

  19. Organic Functional Groups * structures like water

  20. More Organic Functional Groups “carbonyl” compounds

  21. More Organic Functional Groups

  22. Alcohols (organic derivatives of H2O) Nomenclature Alcohols, R-O-H R = CH3 methanol R = CH3CH2 ethanol R = CH3CH2CH2 1-propanol (n-propanol) OH CH3CHCH3 2-propanol (iso-propanol) phenol 3,7-dimethyl-4-octanol

  23. Reactions of Alcohols Oxidation [O] – “H2” primary aldehyde [O] – “H2” secondary ketone [O] No Reaction tertiary [O] = oxidizing agent, e.g. Cr2O72–

  24. More Reactions of Alcohols Elimination + H2O H+ alkene alcohol Substitution RCH2—X RCH2—OH + H—X – H2O alcohol alkyl halide X = Cl, Br, I

  25. Aldehydes and Ketones Nomenclature methanal (formaldehyde) ethanal (acetaldehyde) propanal propanone (acetone) butanone (methyl ethyl ketone) 5-methyl-3-heptanone

  26. Reactions of Aldehydes and Ketones Hydrogenation (reduction) of aldehydes and ketones “H2” primary alcohol aldehyde “H2” secondary alcohol ketone Oxidation of aldehydes (very easy!) [O] aldehyde carboxylic acid

  27. Carboxylic Acids Nomenclature of Acids ethanoic acid (acetic acid) methanoic acid (formic acid) benzoic acid CH3CH2CH2CO2H (condensed formula) butanoic acid Salts of Acids NaOH H2O sodium acetate acetic acid

  28. esters are made by the condensation reaction • between a carboxylic acid and an alcohol • the reaction is acid catalyzed • acid anhydrides are made by the condensation • reaction between 2 carboxylic acid molecules • the reaction is driven by heat Condensation Reactions • a condensation reaction is any organic reaction driven by the removal of a small molecule, like water

  29. Esters Nomenclature of Esters alkyl group acid name ethyl acetate -ate ethyl butanoate methyl benzoate Formation of Esters (from acid + alcohol) + + H2O

  30. Ethers Ethers R – O – R’ CH3CH2–O–CH2CH3 diethyl ether CH3–O–CH2CH2CH3 methyl propyl ether • Ether Synthesis: R–O–H + H–O–R R–O–R H+ – H2O

  31. Amines (organic derivatives of NH3) methylpropylamine methylamine dimethylamine 2-aminohexane aniline Like ammonia, amines are weak bases: RNH2 + H+ RNH3+

  32. Amides Acid derivatives (e.g. 1º amides: –NH2 instead of –OH) H2O + + Nomenclature R = CH3 ethanamide R = CH2CH2CH2CH3 pentanamide, etc. amides (unlike amines) are generally not basic (due to e- withdrawing effect of the C=O group)

  33. Sample Questions (1) Write complete, systematic names for:

  34. Sample Questions, cont. (2) Write complete, specific structural formulas for all of the organic reactants and products in the reaction. an ester sodium acetate + 3-pentanol (3) Show, with specific structures and reactions, how the following compound can be prepared in three steps starting with the appropriate alkyne. NaOH

  35. Answers 1. 2-cyano-4-methyl-3-heptene 2-butylbenzoate 4-phenylhexanal 2. NaOH + 3. cat, D step 1 + H2 pressure + H2O acid cat step 2

  36. Answers, cont. 3., cont. [ox]

  37. Organic Polymers Polymers -- macromolecules made up of many repeating units called monomers e.g. polystyrene is formed via the polymerization of the monomer styrene: e.g. some rings can open to form polymers: hn n ~ 103 - 106 styrene polystyrene

  38. Methods of Polymerization Addition (very common -- works with most alkenes) CH2=CH2 + CH2=CH2 + CH2=CH2 etc…. ---CH2–CH2–CH2–CH2–CH2–CH2--- = • requires an initiator (e.g. a catalyst or UV light) to start the “chain” reaction

  39. More Methods of Polymerization Condensation (common for polyesters and polyamides) a small molecule (e.g. H2O) byproduct is formed X-A-Y + X-B-Y Ring-Opening (uncommon except for polyethers and most inorganic polymers, e.g. silicones) – XY etc…

  40. Common Addition Polymers —CH2–CH2— CH2=CH2 n ethylene polyethylene CH=CH2 —CH–CH2— n styrene polystyrene CH=CH2 —CH–CH2— n Cl Cl vinyl chloride poly(vinyl chloride) ~ PVC CH=CH2 —CH–CH2— n N≡C N≡C cyanoethene “Orlon”

  41. One More Common Addition Polymer! Addition polymerization of dienes “isoprene” (2-methyl-1,3-butadiene) “natural” rubber

  42. Common Condensation Polymers Polyesters + diacid diol – H2O polyester e. g. = = “Dacron”

  43. Sample Question Write a complete structural formula of the organic polymer that is produced in each reaction. State whether the polymerization process is addition, condensation, or ring-opening. + HO-CH2CH2-OH

  44. Answer c. addition a. condensation b. ring-opening d. addition

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