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Chapter 23 “Functional Groups”

Chapter 23 “Functional Groups”. Pre-AP Chemistry Charles Page High School Stephen L. Cotton. Section 23.1 - Introduction to Functional Groups. OBJECTIVES: Explain how organic compounds are classified. Section 23.1 - Introduction to Functional Groups. OBJECTIVES:

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Chapter 23 “Functional Groups”

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  1. Chapter 23“Functional Groups” Pre-AP Chemistry Charles Page High School Stephen L. Cotton

  2. Section 23.1 - Introduction to Functional Groups • OBJECTIVES: • Explain how organic compounds are classified.

  3. Section 23.1 - Introduction to Functional Groups • OBJECTIVES: • Identify halocarbons and the IUPAC rules for naming halocarbons.

  4. Section 23.1 - Introduction to Functional Groups • OBJECTIVES: • Describe how halocarbons can be prepared.

  5. 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

  6. 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.

  7. Functional Groups • The symbol “R” is used to represent any carbon chains or rings • Important: Table 23.1, page 726 -- shows some of the major categories, and their functional groups - KNOW THESE. • Table 23.2, p. 727 - alkyl groups

  8. Halogen Substituents • Halocarbons - class of organic compounds containing covalently bonded fluorine, chlorine, bromine, or iodine • General formula: R-X (X = halogen) • Naming? Name parent as normal, add the halogen as a substituent (or prefix) - Examples on page 726

  9. Halogen Substituents • Common names…p.726 • The more highly halogenated the compound is, the higher the b.p. (see Table 23.3, page 728) • Few halocarbons found in nature • but, readily prepared and used • halothane (Fig. 23.3, p.727) and also the hydrofluorocarbons

  10. 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

  11. 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

  12. Substitution Reactions • Treating benzene with a halogen? Examples on Page 729 • 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 Methanol + sodium chloride

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

  14. Section 23.2Alcohols and Ethers • OBJECTIVES: • Identify how alcohols are classified and named.

  15. Section 23.2Alcohols and Ethers • OBJECTIVES: • Predict how the solubility of an alcohol varies with the length of its carbon chain.

  16. Section 23.2Alcohols and Ethers • OBJECTIVES: • Name the reactions of alkenes that may be used to introduce functional groups.

  17. Section 23.2Alcohols and Ethers • OBJECTIVES: • Construct the general structure of an ether and describe how ethers are named.

  18. 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)

  19. Alcohols • Aliphatic alcohols classified 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 730

  20. 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.

  21. 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 731

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

  23. Alcohols • More than one -OH substituents are called glycols (ethylene glycol?) • ** Examples on page 731 ** • 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

  24. 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

  25. 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 water in all proportions; more than 4 carbons are usually less soluble, because the longer carbon chain is more nonpolar

  26. 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”

  27. 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; also an important industrial solvent

  28. 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!

  29. Addition Reactions • The 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

  30. 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 top of page 734 for the formation of ethanol from ethene + water

  31. Addition Reactions • If a halogen is added in an addition reaction, the result is a halocarbon that is disubstituted - middle p. 734 • The addition of bromine is often used as a test for saturation - p.734 • Addition of a hydrogen halide? -called monosubstituted halocarbon

  32. 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)

  33. Addition Reactions • The hydrogenation of a double bond is a reduction reaction, which in one sense is defined as the “gain of H” • Top- page 735, ethene is “reduced” to ethane; cyclohexene is “reduced” to cyclohexane

  34. 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 735

  35. 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 • Alcohol used for fuel in the future?

  36. Section 23.3Carbonyl Compounds • OBJECTIVES: • Identify the structure of a carbonyl group as found in aldehydes and ketones.

  37. Section 23.3Carbonyl Compounds • OBJECTIVES: • Construct the general formula for carboxylic acids and explain how they are named.

  38. Section 23.3Carbonyl Compounds • OBJECTIVES: • Describe an ester.

  39. Section 23.3Carbonyl Compounds • OBJECTIVES: • Explain how dehydrogenation is an oxidation reaction.

  40. 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

  41. 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!)

  42. Aldehydes and Ketones • Ketones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end) • Structures - bottom of page 737

  43. 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

  44. Aldehydes and Ketones • Table 23.4, page 738 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

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

  46. 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)

  47. The 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

  48. 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 23.6 page 741

  49. The 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

  50. 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

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