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    26sec2 26sec2 Presentation Transcript

    • 26.2 Alcohols and Ethers
    • 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)
    • 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: sec ondary alcohol
        • 3 R groups: tert iary alcohol
      • Note drawings on page 778
    • 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 .
    • 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
    • Alcohols
      • Common names:
        • similar to halocarbons, meaning name the alkyl group, then followed by the word alcohol
        • One carbon alcohol = methyl alcohol
    • 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
    • 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
    • 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
    • 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”
    • 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
    • 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!
    • 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
    • Addition Reactions
      • Addition of water to an alkene is a hydration reaction - usually occurs with heat and an acid (such as HCl or H 2 SO 4 acting as a catalyst)
      • Note sample at top of page 782 for the formation of ethanol from ethene + water
    • Addition Reactions
      • If a halogen is added in an addition reaction, the result is a halocarbon that is disubstituted - middle p. 782
      • The addition of bromine is often used as a test for saturation - p.782
      • Addition of a hydrogen halide? -called monosubstituted halocarbon
    • 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)
    • Addition Reactions
      • The hydrogenation of a double bond is a reduction reaction , which in one sense is defined as the “gain of H”
      • Bottom of page 77,82 ethene is “reduced” to ethane; cyclohexene is “reduced” to cyclohexane
    • 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
    • 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?
    • Ethers
      • Ethers usually have lower boiling pts than alcohols, but higher than hydrocarbons and halocarbons of similar mass
      • Ethers are usually less soluble than alcohols, but more soluble than hydrocarbons and halocarbons
      • Reason for the above: ethers have no hydroxyl group for H-bonding like in alcohols, but do have an oxygen that accepts H