14-1 Chemistry 121, Winter 2012, LA Tech Introduction to Organic Chemistry and Biochemistry Instructor Dr. Upali Siriwardane (Ph.D. Ohio State) Office: 311 Carson Taylor Hall ; Phone: ; Office Hours: MWF 8:00 am - 10:00 am; TT 9:00 – 10:00 am & 1:00-2:00 pm. December 16, 2011 Test 1 (Chapters 12-13) January 20, 2012 Test 2 (Chapters 14,15 & 16) February 6, 2012 Test 3(Chapters 17, 18 & 19) February 27, 2012 Test 4 (Chapters 20, 21 & 22) February 28, 2012 Comprehensive Make Up Exam: Chemistry 121(01) Winter

14-2 Chemistry 121, Winter 2012, LA Tech Chapter 14: Alcohols, Phenols, and Ethers 14.1 Bonding Characteristics of Oxygen Atoms in Organic Compounds 14.2 Structural Characteristics of Alcohols 14.3 Nomenclature for Alcohols 14.4 Isomerism for Alcohols 14.6 Physical Properties of Alcohols 14.7 Preparation of Alcohols 14.8 Classification of Alcohols 14.9 Chemical Reactions of Alcohols Structural Characteristics of Phenols Nomenclature for Phenols Physical and Chemical Properties of Phenols Structural Characteristics of Ethers Nomenclature for Ethers Physical and Chemical Properties of Ethers Sulfur Analogs and Alcohols Sulfur Analogs of Ethers Menthol: A Useful Naturally Occurring Terpene Alcohol; Ethers as General Anesthetics; Marijuana: The Most Commonly Used Illicit Drug; Garlic and Onions: Odiferous Medicinal Plants

14-3 Chemistry 121, Winter 2012, LA Tech Oxygen and Sulfur are Group VIA Elements Has 6 valance electrons Two lone pairs Two lone pairs Two bonding pairs, i.e., it can form two covalent bonds Two bonding pairs, i.e., it can form two covalent bonds Two single or one double bond Two single or one double bond Oxygen and SulfurOxygen and Sulfur

14-4 Chemistry 121, Winter 2012, LA Tech Carbon forms four bonds Hydrogen forms one bond Oxygen and sulfur forms two bonds. Bonding in organic compounds with O and SBonding in organic compounds with O and S

14-5 Chemistry 121, Winter 2012, LA Tech Alcohol: An organic compound in which an — OH group is bonded to a saturated carbon atom. Saturated carbon atom: A carbon atom that is bonded to four other atoms. General structure: R-OH (OH is functional group) Examples: CH 3 OH, C 3 H 7 OH OH in alcohols is not ionic as in NaOH. Alcohols

14-6 Chemistry 121, Winter 2012, LA Tech Alcohols, and Ethers Structures Functional groups: alcohol: R-O-H alcohol: R-O-H phenols: Ar-OH phenols: Ar-OH ether: R-O-R' ether: R-O-R' thiol: R-S-H thiol: R-S-H Alkyl, R = CH 3 Mehtyl etc.

14-7 Chemistry 121, Winter 2012, LA Tech Common Names for Alcohols Common names for Alcohols (C 1 -C 4 alkyl groups). −Rule 1: Name all of the carbon atoms of the molecule as a single alkyl group. − Example: Methyl (C 1 ), Ethyl (C 2 ), propyl (C 3 ) butyl (C 4 ) −Rule 2: Add the word alcohol, separating the worlds with a space. −Examples:

14-8 Chemistry 121, Winter 2012, LA Tech IUPAC Nomenclature of compounds containing functional groups The IUPAC system deals with functional groups two different ways. Modification of the hydrocarbon name to indicate the presence of a functional group. alcohol, -OHuse -ol ending. ether: CH 3 CH 2 -O-CH 3 use methoxy methoxy ethane thiol: R-S-H use -thiol ending.

14-9 Chemistry 121, Winter 2012, LA Tech Alcohol example C - C - C - C - O - H Base contains 4 carbon -alkane name is butane -e -ol -remove -e and add -ol alcohol name - butanol OH is on the first carbon so -1-butanol

14-10 Chemistry 121, Winter 2012, LA Tech Alcohols - Nomenclature Unsaturated alcohols enthe double bond is shown by the infix -en- olthe hydroxyl group is shown by the suffix -ol number the chain to give OH the lower number

14-11 Chemistry 121, Winter 2012, LA Tech Alcohols are classified as primary (1 o ), secondary (2 o ), or tertiary (3 o ) alcohols Primary alcohol (1 o ): Hydroxyl-bearing carbon atom is bonded to only one other carbon atom. Secondary alcohol (2 o ): Hydroxyl bearing carbon atom is bonded to two other carbon atoms. Tertiary alcohol (3 o ): Hydroxyl-bearing carbon atom is bonded to three other carbon atoms. Reactions are dependent on the type of alcohol Alcohols ClassificationAlcohols Classification

14-12 Chemistry 121, Winter 2012, LA Tech Classification of alcohols PrimarySecondaryTertiary.

14-13 Chemistry 121, Winter 2012, LA Tech Alcohols - Nomenclature Examples:

14-14 Chemistry 121, Winter 2012, LA Tech Alcohols - Nomenclature Problem: Write the IUPAC name of each alcohol Octanol 4-methyl-2-pentanol 2-isopropyl cyclohexanol

14-15 Chemistry 121, Winter 2012, LA Tech Common names Ethyl alcohol ethylene glycol glycerol

14-16 Chemistry 121, Winter 2012, LA Tech Diols A diol with two -OH groups attached on two adjacent carbon atoms. Colorless, odorless, miscible in water, great antifreeze, airplane deicer. Extremely toxic. Ethylene Glycol (1,2-Ethanediol) Propylene Glycol (1,2-Propanediol) is nontoxic and is used in drugs as solvent.

14-17 Chemistry 121, Winter 2012, LA Tech Intramolecular Alcohol Dehydration Production of Alkene A dehydration reaction in which the components of water (-H and -OH) are removed from a single reactant Also known as an elimination reaction

14-18 Chemistry 121, Winter 2012, LA Tech Alcohol Dehydration In an intramolecular alcohol dehydration, the components of water (-H and -OH) are removed from neighboring carbon atoms with the resultant introduction of a double bond into the molecule.

14-19 Chemistry 121, Winter 2012, LA Tech Intramolecular Alcohol Dehydration Dehydration of an alcohol can result in more than one alkene product, because hydrogen loss can occur from either of the neighboring carbon atoms. Example: Dehydration of 2-butanol produces two alkenes. Zaitsev’s rule can be used determine the dominant product.

14-20 Chemistry 121, Winter 2012, LA Tech Zaitisev’s Rule The major product formed in an intramolecular alcohol dehydration reaction is the alkene that has the greatest number of alkyl groups attached to the carbon atoms of the double bond. In the following reaction, the predominant product will be 2-butene because the product has CH 3 attached to each carbon atom. OH 2-Butanol H2SO4 180 o C +H 2 O + 1-Butene 2-Butene (Predominant)

14-21 Chemistry 121, Winter 2012, LA Tech Intermolecular Alcohol Dehydration In this reaction, two molecules of alcohol combine to form an ether (Condensation reaction) Only true for primary alcohols and 140 o C. Secondary and tertiary alcohols always give alkene.

14-22 Chemistry 121, Winter 2012, LA Tech Oxidation Addition of oxygen or removal of hydrogen Mild Oxidizing Agents: KMnO 4, K 2 Cr2O7, H2CrO4 Primary and Secondary Alcohols can be oxidized by mild oxidizing agents

14-23 Chemistry 121, Winter 2012, LA Tech Reactivity of 1 ry, 2 ry and 3 ry alcohols: Oxidation of Alcohols

14-24 Chemistry 121, Winter 2012, LA Tech Halogenation Alcohols undergo halogenation reactions In this reaction a halogen atom is substituted for the hydroxyl group producing an alkyl halide. Alkyl halide production by this reaction is superior to alkyl halide production through halogenation of an alkane (PX3: X is Cl or Br)

14-25 Chemistry 121, Winter 2012, LA Tech Constitutional isomerism is possible for alcohols containing three or more carbon atoms. Two types of isomers Skeletal isomers Positional isomers

14-26 Chemistry 121, Winter 2012, LA Tech Alcohol molecules have both polar and nonpolar character. The hydroxyl group is polar part of the molecule The alkyl (R) group is nonpolar part of the molcule The physical properties depend on which portion of the structure “dominates.” Length of the nonpolar carbon chain Number of polar hydroxyl groups Physical PropertiesPhysical Properties

14-27 Chemistry 121, Winter 2012, LA Tech Physical Properties Alcohols are polar compounds both the C-O and O-H bonds are polar covalent

14-28 Chemistry 121, Winter 2012, LA Tech Hydrogen Bonding Figure shows the association of ethanol molecules in the liquid state (only two of the three possible hydrogen bonds to the upper oxygen are shown here).

14-29 Chemistry 121, Winter 2012, LA Tech Boiling Points Alcohols have higher boiling points and are more soluble in water than hydrocarbons

14-30 Chemistry 121, Winter 2012, LA Tech Boiling Points and Solubilities in Water (of selected 1-alcohols)

14-31 Chemistry 121, Winter 2012, LA Tech Combustion reactiond of alcohol Like other hydrocarbons alcohols are also flammable. The combustion products are carbon dioxide and water. 2 CH 3 OH + 4O 2  2CO H 2 O

14-32 Chemistry 121, Winter 2012, LA Tech Conversion of ROH to RX water-soluble 3° alcohols react very rapidly with HCl, HBr, and HI low-molecular-weight 1° and 2° alcohols are unreactive under these conditions

14-33 Chemistry 121, Winter 2012, LA Tech Reaction with SOCl 2 Thionyl chloride, SOCl 2, is the most widely used reagent for conversion of alcohols to alkyl chlorides

14-34 Chemistry 121, Winter 2012, LA Tech Dehydration of Alcohols An alcohol can be converted to an alkene by elimination of H and OH from adjacent carbons (a  -elimination) 1° alcohols must be heated at high temperature in the presence of an acid catalyst, such as H 2 SO 4 or H 3 PO 4 2° alcohols undergo dehydration at somewhat lower temperatures 3° alcohols often require temperatures only at or slightly above room temperature

14-35 Chemistry 121, Winter 2012, LA Tech Dehydration of Alcohols examples:

14-36 Chemistry 121, Winter 2012, LA Tech Hydration-Dehydration Acid-catalyzed hydration of an alkene and dehydration of an alcohol are competing processes large amounts of water favor alcohol formation scarcity of water or experimental conditions where water is removed favor alkene formation

14-37 Chemistry 121, Winter 2012, LA Tech Oxidation of Alcohols to oxidize a 1° alcohol to an aldehyde, use PCC PCC oxidation of geraniol gives geranial Tertiary alcohols are not oxidized by either of these reagents; they are resistant to oxidation

14-38 Chemistry 121, Winter 2012, LA Tech Acidity of Alcohols pK a values for several low-molecular-weight alcohols

14-39 Chemistry 121, Winter 2012, LA Tech Reaction with Active Metals Alcohols react with Li, Na, K, and other active metals to liberate hydrogen gas and form metal alkoxides Na is oxidized to Na + and H + is reduced to H 2 alkoxides are somewhat stronger bases that OH - alkoxides can be used as nucleophiles in nucleophilic substitution reactions they can also be used as bases in  -elimination reactions

14-40 Chemistry 121, Winter 2012, LA Tech Conversion of ROH to RX Conversion of an alcohol to an alkyl halide involves substitution of halogen for -OH at a saturated carbon the most common reagents for this purpose are the halogen acids, HX, and thionyl chloride, SOCl 2

14-41 Chemistry 121, Winter 2012, LA Tech Prepared by hydration of alkenes Alkenes react with water (an unsymmetrical addition agent) in the presence of sulfuric acid (the catalyst) to form an alcohol Markovnikov’s rule is used to determine the predominant alcohol product Preparation of AlcoholsPreparation of Alcohols

14-42 Chemistry 121, Winter 2012, LA Tech

14-43 Chemistry 121, Winter 2012, LA Tech Oxidation of Alcohols Oxidation of a 1° alcohol gives an aldehyde or a carboxylic acid, depending on the oxidizing agent and experimental conditions the most common oxidizing agent is chromic acid chromic acid oxidation of 1-octanol gives octanoic acid

14-44 Chemistry 121, Winter 2012, LA Tech Addition of H 2 to carbonyl (C=O, ). It is similar to adding H 2 to a double bond. In this case one of hydrogen will be added to carbon and the other to oxygen atom of C=O. Addition of H 2 to carbonyl (C=O)

14-45 Chemistry 121, Winter 2012, LA Tech

14-46 Chemistry 121, Winter 2012, LA Tech

14-47 Chemistry 121, Winter 2012, LA Tech

14-48 Chemistry 121, Winter 2012, LA Tech It is possible to synthesize polymeric alcohols with structures similar to those of substituted polyethylenes The simplest polymer is polyvinyl alcohol (PVA) PVA is a tough, whitish polymer that can from strong films, tubes, and fibers that are highly resistant to hydrocarbon solvents Unlike most organic polymers, PVA is water- soluble Polyvinyl alcohol (PVA)Polyvinyl alcohol (PVA)

14-49 Chemistry 121, Winter 2012, LA Tech Phenol: An organic compound in which an —OH group is attached to a carbon atom that is part of an aromatic carbon ring system Aryl group: An aromatic carbon ring system from which one hydrogen atom has been removed. General formula for an aryl alcohol: Ar-OH Substituted phenols: Aryl group substituted with other groups like CH 3, NO 2, etc. Substituted phenol Phenols Phenyl, Ar = C 6 H 5 4-chloro-3-methyl phenol

14-50 Chemistry 121, Winter 2012, LA Tech Phenols: Name “Phenol” is approved by IUPAC Assign the position of the substituent followed by its name and the word phenol Carbon atom with -OH is always number 1 and the other substituents will be assigned minimum possible numbers with reference to hydroxyl carbon IUPAC names of PhenolsIUPAC names of Phenols

14-51 Chemistry 121, Winter 2012, LA Tech Phenols The functional group of a phenol is an -OH group bonded to a benzene ring

14-52 Chemistry 121, Winter 2012, LA Tech Phenols some phenols

14-53 Chemistry 121, Winter 2012, LA Tech Acidity of Phenols Phenols are significantly more acidic than alcohols

14-54 Chemistry 121, Winter 2012, LA Tech Phenols : Low-melting solids or oily liquids at room temperature. Sparingly soluble in water Many phenols have antiseptic and disinfectant properties. The simplest phenol: phenol A colorless solid with a medicinal odor Melting point: 41 o C More soluble in water than any other phenols Properties of PhenolsProperties of Phenols

14-55 Chemistry 121, Winter 2012, LA Tech Acidity of Phenols Unlike alcohols, phenols are weak acids in solution. As acids, phenols have K a values of about M.

14-56 Chemistry 121, Winter 2012, LA Tech Phenols have antiseptic properties 4-hexylresorcinol is an ingredient in many mouthwashes and throat lozenges. o-phenylphenol and 2-benzyl-4-chlorophenol are the active ingredients in Lysol, a disinfectant. Antiseptic Properties of PhenolsAntiseptic Properties of Phenols

14-57 Chemistry 121, Winter 2012, LA Tech Phenols have antioxidant properties: BHA (butylated hydroxy anisole) and BHT (butylated hydroxy toluene) are used as food preservatives to protect it from air oxidation Vitamin E is a phenolic antioxidant A number of phenols found in plants are used as flavoring agents and/or antibacterials. Vanillin is a phenolic which gives flavor of vanilla Antioxidant Properties of PhenolsAntioxidant Properties of Phenols

14-58 Chemistry 121, Winter 2012, LA Tech Ethers: Oxygen bonded to two carbon atoms (functional group) General formula: R-O-R Examples: CH 3 -O-CH 3, CH 3 -O-C 2 H 5 Water and ether have similar structure in that two H of water are replaced by R groups in ethers Ethers

14-59 Chemistry 121, Winter 2012, LA Tech Name the two hydrocarbon groups attached to oxygen atom of the ether and add the word ether The hydrocarbon groups are listed in alphabetical order When both R groups are same than di is used with the name of R group Examples: Earlier “common” naming of ethers

14-60 Chemistry 121, Winter 2012, LA Tech Naming Ethers 2-propoxybutane 2-propoxybutane 2-methoxyphenol 2-methoxyphenol ethoxycyclopropane ethoxycyclopropane isopropyl propyl ether isopropyl propyl ether methyl phenyl ether

14-61 Chemistry 121, Winter 2012, LA Tech Ethers - Nomenclature IUPAC the longest carbon chain is the parent alkane name the -OR group as an alkoxy substituent Common names: ethername the groups bonded to oxygen followed by the word ether

14-62 Chemistry 121, Winter 2012, LA Tech Ethers - Nomenclature Although cyclic ethers have IUPAC names, their common names are more widely used

14-63 Chemistry 121, Winter 2012, LA Tech Ethers - Physical Properties Ethers are polar molecules each C-O bond is polar covalent however, only weak attractive forces exist between ether molecules

14-64 Chemistry 121, Winter 2012, LA Tech Ethers - Physical Properties boiling points are lower than those of alcohols

14-65 Chemistry 121, Winter 2012, LA Tech Ethers - Physical Properties ethers are hydrogen bond donors

14-66 Chemistry 121, Winter 2012, LA Tech Ethers - Physical Properties the effect of hydrogen bonding is illustrated by comparing the boiling points of ethanol and dimethyl ether

14-67 Chemistry 121, Winter 2012, LA Tech Reactions of Ethers Ethers resemble hydrocarbons in their resistance to chemical reaction they do not react with strong oxidizing agents such as chromic acid, H 2 CrO 4 they are not affected by most acids and bases at moderate temperatures Because of their good solvent properties and general inertness to chemical reaction, ethers are excellent solvents in which to carry out organic reactions

14-68 Chemistry 121, Winter 2012, LA Tech Ethers have carbon chains (two alkyl groups ) therefore the constitutional isomerism possibilities in ethers depend on: 1.The partitioning of carbon atoms between the two alkyl groups, and 2.Isomerism possibilities for the individual alkyl groups present. Isomerism is not possible for a C 2 or a C 3 ether C 4 and C 5 ethers exhibit constitutional isomers. Isomerism in Ethers

14-69 Chemistry 121, Winter 2012, LA Tech Functional Group Isomerism Ethers and alcohols with the same number of carbon atoms and the same degree of saturation have the same molecular formula. −For example: Dimethyl ether, and ethyl alcohol both have the molecular formula C 2 H 6 O (constitutional isomers). Functional group isomers are constitutional isomers that contain different functional groups. −C 3 ether–alcohol functional group isomerism possibilities are three (see below)

14-70 Chemistry 121, Winter 2012, LA Tech Chemical properties Ethers are Flammable, e.g., Diethyl ether has boiling point of 35 o C and therefore a flash- fire hazard. Ethers react slowly with oxygen from the air to form unstable hydroperoxides and peroxides. Unreactive towards acids, bases and oxidizing agents (useful for organic reactions) Like alkanes, ethers also undergo halogenation reactions

14-71 Chemistry 121, Winter 2012, LA Tech Cyclic ethers: Contain the ether functional groups as part of a ring system (heterocyclic organic compounds). Heterocyclic organic compound: a cyclic organic compound in which one or more of the carbon atoms in the ring have been replaced with atoms of other elements. Important cyclic ethers: THF : Useful as a solvent in that it dissolves many organic compounds and yet is miscible with water. Polyhydroxy derivatives of the five-membered (furan) and six membered (pyran) carbohydrates are cyclic ether systems Cyclic ethersCyclic ethers

14-72 Chemistry 121, Winter 2012, LA Tech R-SH ---- Thiol R-S-R ---- Thioether Lower boiling point than corresponding alcohols due to lack of hydrogen bonding Strong disagreeable odor Natural gas odor is due to added thiols Thiols and ThiolethersThiols and Thiolethers

14-73 Chemistry 121, Winter 2012, LA Tech Thiols are named in the same way as alcohols in the IUPAC system, except that the “–ol” becomes “-thiol. ” The prefix thio- indicates the substitution of a sulfur atom for an oxygen atom. As in the case of diols and triols, the “-e” at the end of the alkane name is also retained for thiols. Naming Thiols

14-74 Chemistry 121, Winter 2012, LA Tech Properties of Thiols Have lower boiling points than alcohols (lack of hydrogen bonding) Have strong, disagreeable odor The familiar odor of natural gas results from the addition of a low concentration of methanethiol (CH 3 —SH) to the gas. The scent of skunks is due to two thiols. Oxidation of thiols: Lead to disulfide (S-S) bond formation 2 R-SH   R-S-S-R + 2H The above reaction is of biological importance Disulfide bonds formed from two —SH groups aid in protein structure stabilization More reactive than ethers due to weak C-S bond

14-75 Chemistry 121, Winter 2012, LA Tech Thioethers (or sulfides: An organic compound in which a sulfur atom is bonded to two carbon atoms by single bonds. General formula: R—S—R. Like thiols, thioethers (or sulfides) have strong characteristic odors. Thiols are more reactive than their alcohol and ether counterparts. A carbon–sulfur covalent bond is weaker than a carbon–oxygen bond. Dimethyl sulfide is a gas at room temperature and ethyl methyl sulfide is a liquid. Thiols and thioethers exbit functional group isomerism in the same manner that alcohols and ethers. Thioethers and Diulfides Thioethers and Diulfides

14-76 Chemistry 121, Winter 2012, LA Tech Naming thiols

14-77 Chemistry 121, Winter 2012, LA Tech Thiols - Structure The functional group of a thiol is an -SH (sulfhydryl) group bonded to an sp 3 hybridized carbon

14-78 Chemistry 121, Winter 2012, LA Tech Thiols - Nomenclature IUPAC names: the parent chain is the longest chain containing the -SH group thioladd -thiol to the name of the parent chain Common names: mercaptanname the alkyl group bonded to sulfur followed by the word mercaptan mercaptoalternatively, indicate the -SH by the prefix mercapto

14-79 Chemistry 121, Winter 2012, LA Tech Thiols - Physical Properties Low-molecular-weight thiols have a STENCH

14-80 Chemistry 121, Winter 2012, LA Tech Thiols - Physical Properties The difference in electronegativity between S and H is = 0.4 Because of their low polarity, thiols show little association by hydrogen bonding have lower boiling points and are less soluble in water than alcohols of comparable MW