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Topic 10

Topic 10. Organic Chemistry. IB Core Objective. 10.1.1 Describe the features of a homologous series. 10.1.1 Describe the features of a homologous series. Carbon atoms can form long chains.

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Topic 10

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  1. Topic 10 Organic Chemistry

  2. IB Core Objective • 10.1.1 Describe the features of a homologous series.

  3. 10.1.1 Describe the features of a homologous series. • Carbon atoms can form long chains. • These chains can also contain functional groups: which are other atoms such as oxygen, nitrogen or halogens. • Some chains may have the same functional group, but only differ by the presence of additional carbon atoms and associated hydrogen atoms. • These series of compounds that are related are called homologous series.

  4. 10.1.1 Describe the features of a homologous series. Homologous Series • Differ from each other by a CH2 unit. • Can be represented by a general formula (example: alkanes is CnH2n+2) • Compounds have similar chemical properties. • As the number of carbon atoms present increases, the physical properties will vary in a regular manner.

  5. 10.1.1 Describe the features of a homologous series. Alkanes • Alkanes are an example of a homologous series. • Alkanes have the general formula CnH2n+2 • So when using this formula, what kind of bond (single, double, triple) would form between two or more carbons? • A: Single

  6. 10.1.1 Describe the features of a homologous series. Molecular models • Build a methane (CH4) model. • In homologous series, successive compounds differ by a CH2 unit. Build a CH2 unit, and join it with your methane. • What kind of C-C bond does your new molecule have? What would the molecular formula be? Does it follow the CnH2n+2 formula?

  7. IB Core Objective • 10.1.2 Predict and explain the trends in boiling points of members of a homologous series.

  8. 10.1.2 Predict and explain the trends in boiling points of members of a homologous series. • First, lets review van der Waals’ forces. • They are weak forces that attract molecules to each other. • This is caused by random fluctuations in the electron clouds, where they can temporarily produce dipoles. When the overall mass increases, so does the strength of the van der Waals’ forces.

  9. 10.1.2 Predict and explain the trends in boiling points of members of a homologous series. What would happen to the forces of attraction between molecules when the number of carbons in the chain (CH2) are increased? A: The forces of attraction would increase. What happens to the boiling point when forces of attraction increase? A: Boiling point increases as well.

  10. 10.1.2 Predict and explain the trends in boiling points of members of a homologous series.

  11. IB Core Objective • 10.1.3 Distinguish between empirical, molecular and structural formulas.

  12. 10.1.3 Distinguish between empirical, molecular and structural formulas. • Structural • Molecular • Empirical What is the Molecular and empirical formula? Pentanoic Acid H Condensed structural formula H O H H H C C C O C C H CH3(CH2)3COOH H H H H

  13. Writing structures • ‘R’ is sometimes used to represent the carbon chain. • ROH represents the functional group alcohol attached to some carbon chain. • Rings: Benzene Ring (Alternating double bonds)

  14. IB Core Objective • 10.1.4 Describe structural isomers as compounds with the same molecular formula but with different arrangements of atoms.

  15. 10.1.4 Describe structural isomers as compounds with the same molecular formula but with different arrangements of atoms. • Totally different compounds with the same molecular formula • This includes a unique MP and BP • May have totally different chemical properties

  16. Structural Isomers Propanol Primary alcohol MP -127 oC C3H7OH Make a molecular model of both. What is the molecular formula? OH OH Iso-propanol or 2-Propanol Secondary alcohol MP -88oC

  17. IB Core Objectives • 10.1.5 Deduce structural formulas for the isomers of the non-cyclic alkanes up to C6. • 10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6.

  18. 10.1.5 Deduce structural formulas for the isomers of the non-cyclic alkanes up to C6.10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6. Mice Eat Peanut Butter! Or…. Methane, Ethane, Propane, Butane The first four alkanes!

  19. Alkanes • Prefix: Indicates the longest carbon chain. • Ex. Meth - 1 carbon • Eth - 2 • Prop - 3 • But - 4 • Pent - 5 • Hex - 6 • Hept- 7 • Oct- 8 • Non - 9 • Dec- 10 Hydrogen atoms are removed for clarity

  20. Alkanes • Suffix: The ending portion of the name. • All carbon based organic compounds that contain only single bonds have the ending–ane Methane CH4 Ethane CH3CH3 Propane CH3CH2CH3 Butane CH3CH2CH2CH3 Pentane CH3CH2CH2CH2CH3 Hexane CH3CH2CH2CH2CH2CH3

  21. Substituents/ Functional groups Carbon sub chains have the suffix-yl Methyl -CH3 = 1 carbon = meth =Methyl (functional group) • 1st number the carbon chain. In this case no matter which way you go it is a 5 carbon chain, hence pentane. • Next the subgroup must be named, in this case it is a methyl group off of the 4th carbon. BUT the main chain must be numbered closest to the sub group...so you must re-number if you didn’t do it this way. • Name: 2-Methylpentane 2 4 4 1 2 3 5 5 3 1

  22. Multiple Substiuent/Functional Groups Methyl • In this case there are 2 methyl groups on the same carbon. • Name: 2,2-Dimethylpentane 1 –mono 2 –di 3 –tri 4 –tetra 5 –pent 6 –hex 7 –hept 8 –oct 9 –non 10 -dec 4 3 5 2 1 Methyl

  23. Multiple Functional Groups Methyl Methyl • In this case you list the sub groups in alphabetical order first. • Name: 3-Ethyl-3,4-dimethylhexane 5 3 2 1 6 4 di- is used because it indicates 2 of the same functional groups Ethyl

  24. IB Core Objectives • 10.1.9 Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide. • 10.1.10 Apply IUPAC rules for naming compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide.

  25. Functional Groups to Know H C C C C C • -OH (alcohol) • R-CHO (aldehyde) • R-COR (Ketone) • R-COOH (carboxylic acid) • -X (halide) H H H H H H H O O O O Cl Simplified structure R R R O H R

  26. ALCOHOLS If a hydrogen atom of an alkane is replaced by an —OHgroup, the compound is called an Alcohol. Alcohols derived from ALKANES are called ALKANOLS. A functional group is a small set of atoms, held together by covalent bonds in a specific, characteristic arrangement that is responsible for the principal physical and chemical properties of an organic compound.

  27. We interrupt this objective to bring you an all new objective!!

  28. IB Core Objective • 10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes.

  29. Three CLASSES of alcohols occur according to the position of the HYDROXYL, OH, group. The classes of alkanols are: • PRIMARY • SECONDARY • TERTIARY

  30. H H —C—OH R— C—OH H H PRIMARY ALCOHOLS R–CH2– OH HCH2–OH and H Methanol General formula CH3OH

  31. H H H H H H H H H H–C– H–C– C– C– C— C– C — C– C– H H H H H H H H H –C — H H–C–H H PRIMARY ALCOHOLS (cont.) Structural formula for Ethanol (Ethyl Alcohol) : OH 1-butanol: 2-methyl-1-butanol: 1 2 3 4 HO H OH

  32. H H H—C — H—C— H H H H C—H C—H H–C–H H H H —C—OH H H C— C— C — H H SECONDARY ALCOHOLS R´ R2CH—OH R 2-propanol 3-methyl-2-butanol OH OH 2 1 4 3 C5H11OH C3H7OH

  33. H H—C — R´´ H R – C – OH H R´ C—H H H H–C–H C— TERTIARY ALCOHOLS R3COH 2-methyl-2-propanol 1 2 3 OH C4H9OH

  34. 10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes. H H H H H H H H H H H H H H H—C — H–C– H–C– H–C– C– C– C– C C– C– C– C– C– C– H H H H OH H H H O H O H H H H H H –C C– H H OH H H–C– H H H H H H C—H H H H–C–H O H H H H H C— H–C– C–O C–H –C– H H H H ISOMERS of C4H10O PRIMARY ALCOHOLS SECONDARY ALCOHOL TERTIARY ALCOHOL ETHER

  35. Objectives 10.1.9, 10.1.10 Halogenoalkanes An alkane with a halogen (fluorine, chlorine, bromine, or iodine). Often represented by an X, or can include the actual halogen (F, Cl, Br, I) Prefix begins with fluoro-, chloro-, bromo-, or iodo- Example: Name? A: 2-bromo-3-chlorobutane

  36. 10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes. • Primary, secondary and tertiary structures are the same for halgeonoalkanes as alcohols. Describe the difference between primary, secondary and tertiary structures of halgonoalkanes: • Primary: Carbon the halogen is bonded to is bonded to only one other carbon. • Secondary: Carbon the halogen is bonded to is bonded to two other carbons. • Tertiary: Carbon the halogen is bonded to is bonded to three other carbons.

  37. Back to our original objectives • 10.1.9 Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide. • 10.1.10 Apply IUPAC rules for naming compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide.

  38. H R—C— H ALDEHYDES Aldehydes have the suffix –al. ALKANALS are produced by the OXIDATION OF PRIMARY ALCOHOLS (Primary alkanols) RCHO RCH2OH O R—C OH H

  39. H R—C— R´ KETONES ALKANONES are produced by the OXIDATION OF SECONDARY ALCOHOLS (Secondary alkanols) R2CHOH R2CO O OH R— C R´

  40. CARBOXYLIC ACIDS O R — C O–H ALDEHYDES are OXIDISED to CARBOXYLIC ACIDS O O MnO4¯(aq) Carboxyl functional group H3C— C H3C — C H+ + O H – H Ethanoic acid Ethanal (Acetic acid) Aldehyde functional group

  41. IB Core Objectives • 10.1.7 Deduce structural formulas for the isomers of the straight-chain alkenes up to C6. • 10.1.8 Apply IUPAC rules for naming the isomers of the straight-chain alkenes up to C6.

  42. 10.1.7 Deduce structural formulas for the isomers of the straight-chain alkenes up to C6. 10.1.8 Apply IUPAC rules for naming the isomers of the straight-chain alkenes up to C6. Alkenes • General formula: CnH2n • If there are double bonds involved the suffix changes from –ane to –ene. • Molecules are considered un-saturated if there are double bonds present. • After naming the longest chain, number the carbons closest to the double bond

  43. Alkenes • Location of the double bond is important, anything greater than 3 carbons must include a location • Prefix – location – suffix • Pent-1-ene

  44. IB Core Objective • 10.1.11 Identify the following functional groups when present in structural formulas: amino (NH2), benzene ring ( ) and esters (RCOOR).

  45. AMINES • Amines are organic compounds derived from ammonia, NH3. • One or more of the hydrogen atoms are replaced by alkyl groups. • Like alcohols, there can be primary, secondary and tertiary amines.

  46. H H R H H N N N H R N R H R´´ R´ R´ ammonia Primary Amine Secondary Amine Tertiary Amine

  47. N N H H H Amines CH3 methyl amine primary CH3NH2 CH3 dimethyl amine secondary (CH3)2NH CH3

  48. Benzene Six sided ring with alternating double bonds Compounds with benzene are often called aromatic. It is highly flammable with a sweet smell. Phenol Phenylamine

  49. Review of Functional Groups • Alcohol: R-OH (-ol) • Halide: R-X (F, Cl, Br, I) • Ketone: R-CO-R or R2CO • Aldehydes: R-CHO • Benzene: C6H6 • Carboxyl: R-COOH Cl O O O Butanone OH HO H 1- chloropropane Propanoic acid Propanal Benzene Propan-1-ol

  50. O R´– OH R — C O ESTERS + + Carboxylic Acid ESTER Water Alcohol -oate -oic -ol R-COO-R´ O + + H– OH R — C –H O – R´ Water ESTER Carboxylic Acid Alcohol

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