Chapter 26 “Functional Groups and Organic Reactions”

1. Chapter 26“Functional Groups and Organic Reactions”

2. Section 26.1 - Introduction to Functional Groups • OBJECTIVES: • Define a functional group, and give several examples.

3. Section 26.1 - Introduction to Functional Groups • OBJECTIVES: • Describe halocarbons, and the substitution reactions they undergo.

4. Functional Groups • Most organic chemistry involves substituents • often contain O, N, S, or P • also called “functional groups”- they are the chemically functional part of the molecule, and are the non-hydrocarbon part

5. Functional Groups • Functional group - a specific arrangement of atoms in an organic compound, that is capable of characteristic chemical reactions. • What is the best way to classify organic compounds? By their functional groups.

6. Functional Groups • The symbol “R” is used to represent any carbon chains or rings • Important: Table 26.1, page 774 -- shows some of the major categories, and their functional groups - KNOW THESE. • Table 26.2, p. 775 - alkyl groups

7. Halogen Substituents • Halocarbons - class of organic compounds containing covalently bonded fluorine, chlorine, bromine, or iodine • General formula: R-X • Naming? Name parent as normal, add the halogen as a substituent (or prefix) - Examples on page 774

8. Halogen Substituents • The more highly halogenated the compound is, the higher the b.p. (see Table 26.3, page 775) • Few halocarbons found in nature • but, readily prepared and used • halothane (Fig. 26.3, p.776) and also the hydrofluorocarbons

9. Substitution Reactions • Organic reactions often much slower than inorganic reactions • must break strong covalent bond • trying to find new catalysts to use • Substitution - an atom (or group of atoms) replaces another atom or group of atoms

10. Substitution Reactions • A halogen (shown as “X”) can replace a hydrogen to make a halocarbon: R-H + X2 R-X + HX • Sunlight is often a sufficient catalyst: CH4 + Cl2  CH3Cl + HCl UV light

11. Substitution Reactions • Treating benzene with a halogen? Page 776 • Halogens on carbon chains are readily displaced by hydroxide ions (OH1-) to make an alcohol + a salt: R-X + OH1- R-OH + X1- CH3-Cl + NaOH  CH3-OH + NaCl

12. Substitution Reactions CH3-I + KOH  CH3-OH + KI CH3CH2Br + NaOH  CH3CH2OH + NaBr Iodomethane Methanol Bromoethane Ethanol

13. Section 26.2Alcohols and Ethers • OBJECTIVES: • Describe the structures and naming of alcohols and ethers.

14. Section 26.2Alcohols and Ethers • OBJECTIVES: • Define an addition reaction, and give several examples.

15. Section 26.2Alcohols and Ethers • OBJECTIVES: • Compare the properties of alcohols and ethers.

16. Alcohols • Alcohols - a class of organic compounds with an -OH group • The -OH functional group in alcohols is called a “hydroxyl” group; thus R-OH is the formula • How is this different from the hydroxide ion? (covalent bonding with the carbon- not ionic with a metal like bases)

17. Alcohols • Arranged into categories according to the number of R groups attached to the carbon with the hydroxyl • 1 R group: primary alcohol • 2 R groups: secondary alcohol • 3 R groups: tertiary alcohol • Note drawings on page 778

18. Alcohols • Both IUPAC and common names • For IUPAC: • drop the -e ending of the parent alkane name; add ending of -ol, number the position of -OH • parent is the longest chain that contains the carbon with the hydroxyl attached.

19. Alcohols • The hydroxyl is given the lowest position number • Alcohols containing 2, 3, and 4 of the -OH substituents are named diols, triols, and tetrols respectively • Examples on page 779

20. Alcohols • Common names: • similar to halocarbons, meaning name the alkyl group followed by the word alcohol • One carbon alcohol = methyl alcohol

21. Alcohols • More than one -OH substituents are called glycols (ethylene glycol?) • ** Examples on page 779 ** • Phenols - compounds in which a hydroxyl group is attached directly to an aromatic ring. Cresol is the common name of o, m, and p isomers of methylphenol

22. Properties of Alcohols • Much like water, alcohols are capable of hydrogen bonding between molecules • this means they will boil at a higher temp. than alkanes and halocarbons with a comparable number of atoms

23. Properties of Alcohols • Alcohols are derivates of water; the -OH comes from water, and thus are somewhat soluble • Alcohols of up to 4 carbons are soluble in all proportions; more than 4 carbons are usually less soluble, because…?

24. Properties of Alcohols • Many aliphatic alcohols used in laboratories, clinics, and industry • Isopropyl alcohol (2-propanol) is rubbing alcohol; used as antiseptic, and a base for perfume, creams, lotions, and other cosmetics • Ethylene glycol (1,2-ethanediol) - commonly sold as antifreeze

25. Properties of Alcohols • Glycerol (1,2,3-propanetriol) - used as a moistening agent in cosmetics, foods, and drugs; also a component of fats and oils • Ethyl alcohol (ethanol) used in the intoxicating beverages; an important industrial solvent

26. Properties of Alcohols • Denatured alcohol- means it has been made poisonous by the addition of other chemicals, often methyl alcohol (methanol, or wood alcohol). As little as 10 mL of methanol has been known to cause permanent blindness, and 30 ml has resulted in death!!!

27. Addition Reactions • Carbon-carbon single bond is not easy to break • In double bonded alkenes, it is easier to break a bond • Addition reaction- substance is added at the double or triple bond location, after it is broken

28. Addition Reactions • Addition of water to an alkene is a hydration reaction - usually occurs with heat and an acid (such as HCl or H2SO4 acting as a catalyst) • Note sample at bottom of page 781 for the formation of ethanol from ethene + water

29. Addition Reactions • If a halogen is added in an addition reaction, the result is a halocarbon that is disubstituted - top page 782 • The addition of bromine is often used as a test for saturation - p.782 • Addition of a hydrogen halide? -called monosubstituted halocarbon

30. Addition Reactions • Addition of hydrogen to produce an alkane is a hydrogenation reaction, which usually involves a catalyst such as Pt or Pd • common application is the manufacture of margarine from unsaturated vegetable oils (making them solid from a liquid)

31. Addition Reactions • The hydrogenation of a double bond is a reduction reaction, which in one sense is defined as the gain of H • Bottom- page 782, ethene is “reduced” to ethane; cyclohexene is “reduced” to cyclohexane

32. Ethers • A class of organic compounds in which oxygen is bonded to 2 carbon groups: R-O-R is formula • Naming? The two R groups are alphabetized, and followed by ether • Two R groups the same? Use the prefix di- Examples on page 783

33. Ethers • Diethyl ether is the one commonly called just “ether” • was the first reliable general anesthetic • dangerous- highly flammable, also causes nausea • ethers are fairly soluble in water • Note the LINK on page 784

34. Section 26.3Carbonyl Compounds • OBJECTIVES: • Distinguish among the carbonyl groups of aldehydes, ketones, carboxylic acids, and esters.

35. Section 26.3Carbonyl Compounds • OBJECTIVES: • Describe the reactions of compounds that contain the carbonyl functional group.

36. Aldehydes and Ketones • Review: • alcohol has an oxygen bonded to a carbon group and a hydrogen • ether has an oxygen bonded to two carbon groups • An oxygen can also be bonded to a single carbon by a double bond

37. Aldehydes and Ketones • The C=O group is called the “carbonyl group” • it is the functional group in both aldehydes and ketones • Aldehydes - carbonyl group always joined to at least one hydrogen (meaning it is always on the end!)

38. Aldehydes and Ketones • Ketones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end) • Structures - middle of page 785

39. Aldehydes and Ketones • Naming? • Aldehydes: identify longest chain containing the carbonyl group, then the -e ending replaced by -al, such as methanal, ethanal, etc. • Ketones: longest chain w/carbonyl, then new ending of -one; number it • propanone, 2-pentanone, 3-pentanone

40. Aldehydes and Ketones • Table 26.4, page 786 examples • Neither can form intermolecular hydrogen bonds, thus a much lower b.p. than corresponding alcohols • wide variety have been isolated from plants and animals; possible fragrant odor or taste; many common names

41. Aldehydes and Ketones • Benzaldehyde • Cinnamaldehyde • Vanillin • Methanal (common: formaldehyde) • 40% in water is formalin, a preservative

42. Aldehydes and Ketones • Propanone (common: acetone) is a good solvent; miscible with water in all proportions • why is it a good substance used in nail-polish removers? (a powerful solvent-able to dissolve both polar & nonpolar)

43. Carboxylic Acids • Also have a carbonyl group (C=O), but is also attached to a hydroxyl group (-OH) = “carboxyl” group • general formula: R-COOH • weak acids (ionize slightly) • Named by replacing -e with -oic and followed by the word acid • methanoic acid; ethanoic acid

44. Carboxylic Acids • Abundant and widely distributed in nature, many having a Greek or Latin word describing their origin • acetic acid (ethanoic acid) from acetum, meaning vinegar • many that were isolated from fats are called fatty acids • Table 26.6 page 789

45. Esters • General formula: RCOOR • Derivatives of the carboxylic acids, in which the -OH from the carboxyl group is replaced by an -OR from an alcohol: carboxylic acid + alcohol  ester + water • many esters have pleasant, fruity odors- banana, pineapple, perfumes

46. Esters • Although polar, they do not form hydrogen bonds (reason: there is no hydrogen bonded to a highly electronegative atom!) • thus, much lower b.p. than the hydrogen-bonded carboxylic acids they came from

47. Esters • Can be prepared from a carboxylic acid and an alcohol; usually a trace of mineral acid added as catalyst (because acids are dehydrating agents) • Note equation on bottom p. 790

48. Esters • Naming? It has 2 words: • 1st: alkyl attached to single bonded oxygen from alcohol • 2nd: take the acid name, remove the -ic acid, add -ate • example on top of page 791

49. Oxidation- Reduction Reactions • All of the previous classes of organic compounds are related by oxidation and reduction reactions • What is oxidation-reduction? • Oxidation: the gain of oxygen, loss of hydrogen, or loss of e-1 • Reduction: the loss of oxygen, gain of hydrogen, or gain of e-1

50. Oxidation- Reduction Reactions • Oxidation and reduction reactions (sometimes called redox) are coupled- one does not occur without the other • The number of Oxygen and Hydrogen attached to Carbon indicates the degree of oxidation