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Chapter 25 Organic Chemistry I: Compounds Chapter Goals Saturated Hydrocarbons 1. Alkanes and Cycloalkanes 2. Naming Saturated Hydrocarbons Unsaturated Hydrocarbons 3. Alkenes 4. Alkynes Aromatic Hydrocarbons 5. Benzene 6. Other Aromatic Hydrocarbons 7. Hydrocarbons: A Summary 2 Chapter Goals Functional Groups 8. Organic Halides 9. Alcohols and Phenols 10.Ethers 11.Aldehydes and Ketones 12.Amines 13.Carboxylic Acids 14.Some Derivatives of Carboxylic Acids 15.Summary of Functional Groups 3 Chapter Goals Fundamental Classes of Organic Reactions 16.Substitution Reactions 17.Addition Reactions 18.Elimination Reactions 19.Polymerization Reactions 4 Saturated Hydrocarbons Hydrocarbons are chemical compounds that contain only C and H atoms. Saturated hydrocarbons contain only single or sigma () bonds. There are no double or triple bonds in these compounds. The primary source of hydrocarbons is petroleum and natural gas. 5 Alkanes and Cycloalkanes The simplest saturated hydrocarbons are called alkanes. Methane, CH4, is the simplest alkane. The alkanes form a homologous series. Each member of the series differs by a specific number and kind of atoms. H C H H H or CH4 6 Alkanes and Cycloalkanes The alkanes differ from each other by a CH2 or methylene group. All alkanes have this general formula. CnH2n+2 For example ethane, C2H6 , and propane, C3H8 , are the next two family members. H H H C H H H H C C H H C2H6 H H H H H C C C H H H H H H C H H C3H8 7 Alkanes and Cycloalkanes Isomers are chemical compounds that have the same molecular formulas but different structures. Two alkanes have the molecular formula C4H10. They are a specific type of isomer called structural isomers. H H H H H H H H C C C C H H H H H C C C H H H H H C H H H C H H n-butane H H H C H H 2-methylpropane 8 Alkanes and Cycloalkanes Three alkanes have the formula C5H12. There are three structural isomers of pentane. H3C H2 C C H2 H2 C CH3 n-pentane 9 Alkanes and Cycloalkanes Three alkanes have the formula C5H12. There are three structural isomers of pentane. H3C H2 C C H2 H2 C n-pentane CH3 CH3 CH3 C H3C H C H2 2-methylbutane 10 Alkanes and Cycloalkanes Three alkanes have the formula C5H12. There are three structural isomers of pentane. H2 C H3C C H2 H2 C H H C H H CH3 CH CH3 H3C C H2 CH3 CH3 H n-pentane H C H H C H3C CH3 CH3 H 2-methylbutane H C H H 2,2-dimethylpropane 11 Alkanes and Cycloalkanes There are five isomeric hexanes, C6H14. You draw them! H3C H2 C C H2 H2 C C H2 CH3 n-hexane 12 Alkanes and Cycloalkanes There are five isomeric hexanes, C6H14. H3C H2 C C H2 H2 C CH3 C H2 n-hexane CH3 C H3C H C H2 H2 C CH3 2-methylpentane 13 Alkanes and Cycloalkanes There are five isomeric hexanes, C6H14. H3C H2 C C H2 H2 C CH3 C H2 n-hexane CH3 C H3C H C H2 H2 C CH3 2-methylpentane H2 H2 C H C CH3 C H3C CH3 3-methylpentane 14 Alkanes and Cycloalkanes There are five isomeric hexanes, C6H14. H3C H2 C C H2 H2 C CH3 C H2 CH3 n-hexane C H3C H C H2 H2 C CH3 2-methylpentane H2 H2 C H C CH3 C H3C CH3 3-methylpentane CH3 C H2 CH3 C H3C CH3 2,2-dimethylbutane 15 Alkanes and Cycloalkanes There are five isomeric hexanes, C6H14. H3C H2 C C H2 H2 C CH3 C H2 CH3 C H3C H C H2 H2 C CH3 n-hexane 2-methylpentane CH3 C H2 CH3 C H3C CH3 CH3 C H CH3 H3C H C 2,2-dimethylbutane 2,3-dimethylbutane H2 H2 C H C CH3 C H3C CH3 3-methylpentane CH3 16 Alkanes and Cycloalkanes The number of structural isomers increases rapidly with increasing numbers of carbon atoms. The boiling points of the alkanes increase with molecular weight. 17 Alkanes and Cycloalkanes Cyclic saturated hydrocarbons are called cycloalkanes. They have the general formula CnH2n. Some examples are: H2 C H2C CH2 C C H2 H2 cyclopentane 18 Alkanes and Cycloalkanes Cyclic saturated hydrocarbons are called cycloalkanes. They have the general formula CnH2n. Some examples are: H2 C H2C CH2 C C H2 H2 cyclopentane H2C H2C H2 C C H2 CH2 CH2 cyclohexane 19 Alkanes and Cycloalkanes Cyclic saturated hydrocarbons are called cycloalkanes. They have the general formula CnH2n. Some examples are: H2C H2C H H C H H H2 H2 C C H2 C H2 C CH 2 CH 2 cyclopentane H2C CH 2 H2C CH 2 H2C CH 2 H2C H2C CH 2 C H2 H H C H H CH 2 H cyclohexane H C H H cyclooctane 20 Naming Saturated Hydrocarbons The International Union of Pure and Applied Chemistry (IUPAC) names for the first 12 "straight-chain" or "normal" alkanes are given in this table. Number of carbon atoms in chain Name 1 Methane 2 Ethane 3 Propane 4 Butane 5 Pentane 6 Hexane 21 Naming Saturated Hydrocarbons Number of carbon atoms in chain Name 7 Heptane 8 Octane 9 Nonane 10 Decane 11 Unidecane 12 Dodecane 22 Naming Saturated Hydrocarbons Other organic compounds are named as derivatives of the alkanes. Branched-chain alkanes are named by the following rules. 1. Choose the longest continuous chain of carbon atoms which gives the basic name or stem. 23 Naming Saturated Hydrocarbons 2 3 Number each carbon atom in the basic chain, starting at the end that gives the lowest number to the first group attached to the main chain (substituent). For each substituent on the chain, we indicate the position in the chain (by an Arabic numeric prefix) and the kind of substituent (by its name). The position of a substituent on the chain is indicated by the lowest number possible. The number precedes the name of the substituent. 24 Naming Saturated Hydrocarbons 4 When there are two or more substituents of a given kind, use prefixes to indicate the number of substituents. di = 2, tri = 3, tetra = 4, penta = 5, hexa = 6, hepta = 7, octa = 8, and so on. 5 The combined substituent numbers and names serve as a prefix for the basic hydrocarbon name. 6 Separate numbers from numbers by commas and numbers from words by hyphens. Words are "run together". 25 Naming Saturated Hydrocarbons Alkyl groups (represented by the symbol R) are common substituents. Alkyl groups are fragments of alkanes in which one H atom has been removed for the connection to the main chain. Alkyl groups have the general formula CnH2n+1. In alkyl groups the -ane suffix in the name of the parent alkane is replaced by -yl. A one carbon group is named methyl. A two carbon group is named ethyl. A three carbon group is named propyl. 26 Unsaturated Hydrocarbons The three classes of unsaturated hydrocarbons are: 1. alkenes and cycloalkenes, CnH2n 2. alkynes and cycloalkynes, CnH2n-2 3. aromatic hydrocarbons 27 Alkenes The simplest alkenes contain one C=C bond per molecule. The general formula for simple alkenes is CnH2n. The first two alkenes are: ethene, C2H4 H H C C H H C H H H H 28 Alkenes The simplest alkenes contain one C=C bond per molecule. The general formula for simple alkenes is CnH2n. The first two alkenes are: and propene, C3H6 H H H H C H H C H C H H C H 29 Alkenes Each doubly bonded C atom is sp2 hybridized. The sp2 hybrid consists of: two bonds (single bonds) and one and one p bond (double bond) 30 Alkenes The systematic naming system for alkenes uses the same stems as alkanes. In the IUPAC system, the -ane suffix for alkanes is changed to -ene. Common names for the alkenes have the same stem but use the suffix -ylene is used. In chains of four or more C atoms, a numerical prefix shows the position of the lowest-numbered doubly bonded C atom. Always choose the longest chain that contains the C=C bond. 31 Alkenes Polyenes contain two or more double bonds per molecule. Indicate the number of double bonds with suffixes: -adiene for two double bonds. -atriene for three double bonds, etc. The positions of the substituents are indicated as for alkanes. The position of the C=C bond(s) is/are given the lowest number(s) possible. 32 Alkenes H H C C H H C H C H H C H C H H 1,3-hexadiene 33 Alkenes H H C C H H H C H H H H C C H H C H C H H 1,3-hexadiene H H H H C C C C C C H H H H H H C H H 1,3,5-hexatriene 34 Alkenes H H C C H H C H C H H C H C H H H C H H H H C C C C H C H H 1,3,5-hexatriene 1,3-hexadiene H H H C H H H C H C C C C C H H H C H H 2,3-dimethyl-1,3,5-hexatriene 35 Cycloalkenes Cycloalkenes have the general formula CnH2n-2. Examples are: cyclopentene H H H C C H H C C H H H C 36 Cycloalkenes cyclohexene H H H C C H C H C C H C H H H H 37 Cycloalkenes cycloheptene H H H H C C H C H C H C H C C H H H H 38 Alkynes Alkynes contain CC bonds. The simplest alkyne is C2H2, ethyne, or acetylene. Alkynes with only one C C bond have the formula CnH2n-2. Each carbon atom in a C C bond is sp hybridized. Each sp hybrid contains two bonds and two p bonds. The carbon atom will have one single bond and one triple bond. 39 Alkynes Alkynes are named like the alkenes except that the suffix -yne is used with the characteristic stem The alkyne stem is derived from the name of the alkane with the same number of carbon atoms. H H H C C H H C C H H H C C C H H H H H C H H H H H C C H C H H H H H C C C C C H H H H H H H 3-heptyne H C H H 2-octyne 40 Alkynes Acetylene is an important industrial chemical. It is prepared by the reaction of calcium carbide with water. CaC2 s H 2O C2 H 2 g CaOs 41 Alkynes Acetylene burns in a highly exothermic reaction The combustion produces temperatures of about 3000°C. Acetylene is used in cutting torches for welding. 2C2 H 2 g 5O2 g 4CO2 g 2 H 2Og Alkynes are very reactive The two p bonds are sights of special reactivity. Addition reactions, such as hydrogenation, are common. C2 H 2 g 2H 2 g C2 H 6 g 42 Hydrocarbons: A Summary Carbon Atom Hybridization sp3 tetrahedral sp2 trigonal planar sp linear C uses C forms Example 4 bonds CH4 3 hybrids & 1p orbital 3 bonds 1 p bond C2H 4 2 sp hybrids & 2 p orbitals 2 bonds 2p bonds C2H 2 4 sp3 hybrids sp2 43 Aromatic Hydrocarbons Historically, aromatic was used to describe pleasant smelling substances. Now it refers to benzene, C6H6, and derivatives of benzene. Other compounds that have similar chemical properties to benzene are also called aromatic. 44 Benzene The structure of benzene, C6H6, is: H H H H H C H H C C C C C C H H H 45 Other Aromatic Hydrocarbons Coal tar is the common source of benzene and many other aromatic compounds. Some aromatic hydrocarbons that contain fused rings are: H H napthalene H H H H C H H C C C C H C C C C C C H H H 46 Other Aromatic Hydrocarbons phenanthrene H H H H C C C C H H C C C C C C C C C C H H H H 47 Other Aromatic Hydrocarbons Many aromatic hydrocarbons contain alkyl groups attached to benzene rings (as well as to other aromatic rings). The positions of the substituents on benzene rings are indicated by the prefixes: ortho- (o-) for substituents on adjacent C atoms meta- (m-) for substituents on C atoms 1 and 3 para- (p-) for substituents on C atoms 1 and 4 48 Other Aromatic Hydrocarbons CH 3 CH3 CH 3 CH 3 CH3 H H C H H m-xylene CH 3 H H C H H o-xylene H H C H H p-xylene 49 Functional Groups Functional groups are groups of atoms that represent potential reaction sites. Compounds that contain a given functional group usually undergo similar reactions. Functional groups influence physical properties as well. 50 Organic Halides A halogen atom may replace almost any hydrogen atom in a hydrocarbon. The functional group is the halide (-X) group. Examples include: chloroform, CHCl3 Cl Cl C H Cl 51 Organic Halides 1,2-dichloroethane, ClCH2CH2Cl H Cl H C C H H H C H H Cl H 52 Organic Halides para-dichlorobenzene Cl Cl 53 Alcohols and Phenols The functional group in alcohols and phenols is the hydroxyl (-OH) group. Alcohols and phenols can be considered derivatives of hydrocarbons in which one or more H atoms have been replaced by -OH groups. Phenols are derivatives of benzene in which one H has been replaced by replaced by -OH group. 54 Alcohols and Phenols Ethyl alcohol (ethanol), C2H5OH, is the most familiar alcohol. H H H C C OH H H C H H H H 55 Alcohols and Phenols Phenol, C6H5OH, is the most familiar phenol. OH 56 Alcohols and Phenols Alcohols are considered neutral compounds because they are only very slightly acidic. Alcohols can behave as acids but only in the presence of very strong bases. Phenols are weakly acidic. Ka 1.0 x 10-10 for phenol Although phenols are very weakly acidic, they are also very corrosive. 57 Alcohols and Phenols Alcohols can be classified into three classes: 1. Primary (1°) alcohols like ethanol have the -OH group attached to a C atom that has one bond to another C atom. H3C C OH H2 58 Alcohols and Phenols 2. Secondary(2°) alcohols have the –OH group attached to a C atom that has bonds to 2 other C atoms. For example,2-propanol: H3C HC OH H3C 59 Alcohols and Phenols 3. Tertiary (3°) alcohols have the –OH group attached to a C atom that is bonded to 3 other C atoms. For example, 2-methyl-2-propanol OH H3C C CH3 CH3 60 Alcohols and Phenols The stem for the parent hydrocarbon plus an -ol suffix is the systematic name for an alcohol. A numeric prefix indicates the position of the -OH group in alcohols with three or more C atoms. Common names are the name of the appropriate alkyl group plus alcohol. 61 Alcohols and Phenols Alcohols are named using the stem for the parent hydrocarbon plus an -ol suffix in the systematic nomenclature. A numeric prefix indicates the position of the -OH group in alcohols with three or more C atoms. Common alcohol names are the name of the appropriate alkyl group plus the word alcohol. H2C H22 C OH C C H22 H H222 H C C OH OH CH333 CH 1-pentanol 1-pentanol 1-pentyl alcohol C C H C H33C C H C H H22 H H22 H C C CH33 CH 2-pentanol 2-pentanol 2-pentyl alcohol alcohol 2-pentyl H2 H2 C H C H3C C CH3 OH 3-pentanol 62 3-pentyl alcohol Alcohols and Phenols There are several isomeric monohydric acyclic (contains no rings) alcohols that contain more than three C atoms. There are four isomeric four-carbon alcohols. 63 Alcohols and Phenols OH H2 C HO H H C H H H2 C C H2 CH H3C CH3 CH 3 H 1-butanol H C H H 2-butanol OH HO CH 2 H3C CH H3C CH 2 C CH 3 CH 3 CH 3 H H H C H H 2-methyl-1-propanol H C H H 2-methyl-2-propanol 64 Alcohols and Phenols OH H2 C H2 C H2 C H2 H2 C H C CH3 C H3C There are eight isomericC five-carbon alcohols. CH C C CH HC H C H H OH You Hdo it! HO 3 3 3 2 2 2 1-pentanol 2-pentanol CH3 HO 2-methyl-1-butanol CH3 C H3C H C H2 H2 C CH3 CH3 CH3 C C HC H2 H2 H3C 3-pentanol C CH2 OH CH3 2-methyl-2-butanol C H CH3 H3C H C OH 3-methyl-2-butanol CH3H 2 OH 3-methyl-1-butanol H3C C C CH3 OH 2,2-dimethyl-1-propanol 65 Alcohols and Phenols Polyhydric alcohols contain more than one -OH group per molecule. OH OH C H2C H CH2 OH OH glycerin HO OH OH C H C H CH2 C H C H C H2 OH OH sorbitol 66 Alcohols and Phenols Phenols are usually called by their common (trivial) names. OH OH resorcinol 67 Alcohols and Phenols Phenols are usually called by their common (trivial) names. OH OH CH3 OH resorcinol o-cresol 68 Alcohols and Phenols Phenols are usually called by their common (trivial) names. OH OH OH CH3 CH3 OH resorcinol o-cresol m-cresol 69 Alcohols and Phenols Phenols are usually called by their common (trivial) names. OH OH OH OH CH3 CH3 OH resorcinol o-cresol m-cresol CH3 p-cresol 70 Alcohols and Phenols Because the -OH group is quite polar, the properties of alcohols depend upon the number of -OH groups per molecule and the size of the organic group. The boiling points of monohydric alcohols increase with increasing molecular weight. The solubility of monohydric alcohols in water decrease with increasing molecular weight. Polyhydric alcohols are more soluble in water because of the two or more polar groups (-OH). 71 Ethers Ethers may be thought of as derivatives of water in which both H atoms have been replaced by alkyl or aryl groups. H O H water 72 Ethers Ethers may be thought of as derivatives of water in which both H atoms have been replaced by alkyl or aryl groups. H O H water H3C O H an alcohol 73 Ethers Ethers may be thought of as derivatives of water in which both H atoms have been replaced by alkyl or aryl groups. H O H water H3C O H an alcohol H3C O CH3 an ether 74 Ethers Ethers are not very polar and not very reactive. They are excellent solvents. Common names are used for most ethers. H3C O C H2 CH3 H3C O CH3 H2 C H3C O H2 C CH3 H H H C H H ethylmethyl ether H C H H dimethyl ether H H C H H diethyl ether 75 Aldehydes and Ketones The functional group in aldehydes and ketones is the carbonyl group. O R1 R2 or H carbonyl group 76 Aldehydes and Ketones Except for formaldehyde, aldehydes have one H atom and one organic group bonded to a carbonyl group. O H3C H H C H H O O H ethanal or acetaldehyde H H H C H H H3C H methanal or formaldehyde H H C H H C H2 H propanal or propionaldehyde 77 Aldehydes and Ketones Ketones have two organic groups bonded to a carbonyl group. O O C C H3C H H C H H O H2C CH 3 propanone or acetone C CH 3 H 2C CH 3 H H C H H 2-butanone or ethylmethylketone CH 3 H H C H H CH 2 CH 3 3-pentanone or diethylketone 78 Aldehydes and Ketones Common names for aldehydes are derived from the name of the acid with the same number of C atoms. IUPAC names are derived from the parent hydrocarbon name by replacing -e with -al. H3C C H2 H2 C O C H2 C H pentanal or pentyl aldehyde 79 Aldehydes and Ketones Common names for aldehydes are derived from the name of the acid with the same number of C atoms. IUPAC names are derived from the parent hydrocarbon name by replacing -e with -al. H3C C H2 H2 C O O C H2 C pentanal or pentyl aldehyde H3C H H3C C C H CH3 2,3-dimethylproponal or 2,3-dimethylpropionaldehyde 80 Aldehydes and Ketones Common names for aldehydes are derived from the name of the acid with the same number of C atoms. IUPAC names are derived from the parent hydrocarbon name by replacing -e with -al. H3C C H2 H2 C O C H2 C pentanal or pentyl aldehyde H3C H H3C C O O C C H H CH3 2,3-dimethylproponal or 2,3-dimethylpropionaldehyde benzanal or benzyl aldehyde 81 Aldehydes and Ketones The IUPAC name for a ketone is the characteristic stem for the parent hydrocarbon plus the suffix -one. A numeric prefix indicates the position of the carbonyl group in a chain or on a ring. H3C C H2 H2 C O C H2 C CH3 2-hexanone or methyl pentyl ketone 82 Aldehydes and Ketones The IUPAC name for a ketone is the characteristic stem for the parent hydrocarbon plus the suffix -one. A numeric prefix indicates the position of the carbonyl group in a chain or on a ring. H3C C H2 H2 C O C H2 C CH3 2-hexanone or methyl pentyl ketone H3C H2 C O C H2 C C H2 CH3 3-hexanone or ethyl propyl ketone 83 Aldehydes and Ketones The IUPAC name for a ketone is the characteristic stem for the parent hydrocarbon plus the suffix -one. A numeric prefix indicates the position of the carbonyl group in a chain or on a ring. O H3C C H2 H2 C O C H2 C CH3 2-hexanone or methyl pentyl ketone H3C H2 C O C H2 C C H2 C CH3 CH3 3-hexanone or ethyl propyl ketone acetophenone or methyl phenyl ketone 84 Aldehydes and Ketones Many aldehydes and ketones occur in nature. H HC C O CH3 OH CH CH3 O cinnamaldehyde testosterone 85 Amines Amines are derivatives of ammonia in which one or more H atoms have been replaced by organic groups (aliphatic or aromatic or a mixture of both). There are three classes of amines. H N H H ammonia 86 Amines Amines are derivatives of ammonia in which one or more H atoms have been replaced by organic groups (aliphatic or aromatic or a mixture of both). There are three classes of amines. H N H H ammonia H3C N H H primary amine 87 Amines Amines are derivatives of ammonia in which one or more H atoms have been replaced by organic groups (aliphatic or aromatic or a mixture of both). There are three classes of amines. H N H H ammonia H3C N H primary amine H H3C N H CH3 secondary amine 88 Amines Amines are derivatives of ammonia in which one or more H atoms have been replaced by organic groups (aliphatic or aromatic or a mixture of both). There are three classes of amines. H N H H ammonia H3C N H primary amine H H3C N H CH3 secondary amine H3C N CH3 CH3 tertiary amine 89 Amines Aniline is the simplest aromatic amine. It is much less basic than NH3. Aniline is a very important industrial chemical. NH 2 H H C H H aniline 90 Amines Heterocylic amines have one or more N atoms in a ring structure. Many are important in living systems. N pyridine 91 Amines Heterocylic amines have one or more N atoms in a ring structure. Many are important in living systems. N N pyridine N pyrimidine 92 Amines Heterocylic amines have one or more N atoms in a ring structure. Many are important in living systems. N N pyridine N N N pyrimidine N N purine 93 Carboxylic Acids Carboxylic acids contain the carboxyl functional group. O C OH The general formula for carboxylic acids is: R represents an alkyl or an aryl group O C R1 OH 94 Carboxylic Acids IUPAC names for a carboxylic acid are derived from the name of the parent hydrocarbon. The final -e is dropped from the name of the parent hydrocarbon The suffix -oic is added followed by the word acid. Many organic acids are called by their common (trivial) names which are derived from Greek or Latin. 95 Carboxylic Acids O O C C H H H C H H H3C OH methanoic acid or formic acid H H C H H OH ethanoic acid or acetic acid O H 3C H H C H H O H2 C C C H2 OH propanoic acid or propionic acid H3C H H C H H C C H2 OH butanoic acid or butyric acid 96 Carboxylic Acids Positions of substituents on carboxylic acid chains are indicated by numeric prefixes as in other compounds Begin the counting scheme from the carboxyl group carbon atom. They are also often indicated by lower case Greek letters. = 1st C atom = 2nd C atom = 3rd C atom, etc. 97 Carboxylic Acids O H3C H C C OH CH3 2-methylpropanoic acid or -methylpropanoic acid 98 Carboxylic Acids O H3C H C C OH CH3 CH3 O C C OH H3C H C H2 2-methylpropanoic acid 3-methylbutanoic acid or or -methylpropanoic acid -methylbutanoic acid 99 Carboxylic Acids O H3C H C C OH CH3 CH3 O C C OH H3C H C H2 2-methylpropanoic acid 3-methylbutanoic acid or or -methylpropanoic acid -methylbutanoic acid O H2 H3C H C C C C OH H2 CH3 4-methylpentanoic acid or -methylpentanoic acid 100 Carboxylic Acids Dicarboxylic acids contain two carboxyl groups per molecule. O OH C C HO O oxalic acid 101 Nomenclature of Carboxylic Acids Dicarboxylic acids contain two carboxyl groups per molecule. O O O OH C C HO O oxalic acid HO C C H2 C OH malonic acid 102 Nomenclature of Carboxylic Acids Dicarboxylic acids contain two carboxyl groups per molecule. O O O H2 O OH OH C C C C C C C C HO OH C HO H2 HO O H2 O succinic acid malonic acid oxalic acid 103 Carboxylic Acids Aromatic acids are usually called by their common names. Sometimes, they are named as derivatives of benzoic acid which is considered to be the "parent" aromatic acid. 104 Carboxylic Acids HO HO O O benzoic acid Cl p-chlorobenzoic acid 105 Carboxylic Acids HO HO benzoic acid HO O O O Cl p-chlorobenzoic acid OH O OH CH3 p-toluic acid O phthalic acid 106 Carboxylic Acids Acid strengths of simple carboxylic acids vary little with chain length. However, substituents on a carbon atom in the chain can cause large variations in acid strengths . 107 Carboxylic Acids Compound Name Ka formic acid 1.8 x 10-4 acetic acid 1.8 x 10-5 propionic acid 1.4 x 10-5 O H C OH O H3C C OH O H3C C H2 C OH 108 Carboxylic Acids Compound O H3C C Name Ka acetic acid 1.8 x 10-5 monochloroacetic acid 1.5 x 10-3 dichloroacetic acid 5.0 x 10-2 trichloroacetic acid 2.0 x 10-1 OH O Cl C H2 C OH O Cl H C C OH Cl O Cl Cl C C OH Cl 109 Carboxylic Acids The -OH group in the carboxyl group of carboxylic acids, is displaced in many of their reactions. The non -OH portion of a carboxylic acid is called an acyl group. R1 O O C C OH carboxyl group R1 acyl group 110 Some Derivatives of Carboxylic Acids Four important classes of compounds contain acyl groups They are all considered to be derivatives of carboxylic acids. In these structures R's may represent either alkyl or aryl groups. 111 Some Derivatives of Carboxylic Acids R1 O O O C C C O R1 acid anhydride R1 Cl acid chloride 112 Some Derivatives of Carboxylic Acids R1 O O O C C C O R1 acid anhydride R1 acid chloride O O R1 C Cl O ester R2 R1 C NH2 amide 113 Some Derivatives of Carboxylic Acids Acid anhydrides are related to their parent acids as follows: The word anhydride means without water. O 2 H3C C O O OH acetic acid H3C O CH3 + H2O acetic anhydride 114 Some Derivatives of Carboxylic Acids Acyl halides are much more reactive, and more volatile, than their parent acids. They react with water to form their parent acids and a hydrohalic acid. O H3C C O Cl acetyl chloride + H2O H3C OH + HCl acetic acid 115 Some Derivatives of Carboxylic Acids Acyl halides are prepared by reacting their parent acids with PCl3, PCl5, or SOCl2. The more volatile acid halide is then distilled out of the reaction mixture. HO O Cl O + benzoic acid PCl5 benzoyl chloride 116 Some Derivatives of Carboxylic Acids Esters are prepared by heating a carboxylic acid with an alcohol in the presence of a small amount of an inorganic acid. The reaction mixture will contain some ester and water, as well as unreacted acid and alcohol. O H3C C OH ethanoic acid or acetic acid + H3C C H2 OH ethanol or ethyl alcohol H2SO4 O H3C C O H2 C + H2O CH3 ethyl ethanoate or ethyl acetate 117 Some Derivatives of Carboxylic Acids Esters are usually called by their common names. Many simple esters occur naturally and have pleasant odors. Esters are frequently used in fragrances and as artificial flavors. H3C H2 C O C H2 C O H2 C O CH3 ethyl butanoate or ethyl butyrate odor of pineapples H3C O H2 C C H2 H2 C C H2 H2 C C H2 H2 C CH3 octyl ethanoate or octyl acetate odor of oranges 118 Some Derivatives of Carboxylic Acids Fats are solid esters of glycerol and (mostly) saturated acids at room temperature. Oils are liquid esters of glycerol and primarily unsaturated acids at room temperature. The "acid" parts of fats and oils usually contain even numbers of C atoms in naturally occurring fats and oils. 16 and 18 carbon chains are the most commonly found chain sizes in nature. 119 Some Derivatives of Carboxylic Acids Some acids that are found (as their esters) in fats and oils include: H3C H2 C C H2 H2 C C H2 H2 C C H2 H2 C C H2 H2 C C H2 H2 C C H2 H2 C O C H2 C OH palmitic acid CH3(CH2)14COOH 120 Some Derivatives of Carboxylic Acids Stearic acid is often found in beef fat. H3C H2 C C H2 H2 C C H2 H2 C C H2 H2 C C H2 H2 C C H2 H2 C C H2 H2 C C H2 H2 C O C H2 C OH stearic acid CH3(CH2)16COOH 121 Some Derivatives of Carboxylic Acids Triglycerides are the triesters of glycerol. The common name for triglycerides is tri (acid stem) plus an -in suffix. For example, tripalmitin. (CH2)14CH3 O OH C O H2C CH HO OH + 3 CH3(CH2)14COOH H2C CH CH 2 O glycerin palmitic acid O H H C H H C O CH 2 C (CH2)14CH3 O (CH2)14CH3 tripalmitin 122 Some Derivatives of Carboxylic Acids Waxes are esters of long chain fatty acids and alcohols other than glycerol. Commonly, waxes are derived from monohydric alcohols. Beeswax and carnauba wax are esters of myricyl alcohol, C30H61OH. 123 Some Derivatives of Carboxylic Acids Carnauba wax is often used in car waxes. O C25H51 C O C30H61 carnauba wax 124 Some Derivatives of Carboxylic Acids Dihydric alcohols (2 –OH’s per molecule) can react with dicarboxylic acids (2 –COOH’s per molecule) to form polyesters. Ester linkages are formed at both ends of both molecules to give polymeric esters with very high molecular weights. OH O C + C O HO terephthalic acid dicarboxylic acid H2 H2 C C HO OH ethylene glycol dihydric alcohol 125 Some Derivatives of Carboxylic Acids * n * O O O C CH2 H2C C O O dacron 126 Some Derivatives of Carboxylic Acids Amides are derivatives of organic acids and primary or secondary amines. The functional groups of amides are: O R1 C O N H H or R1 C O N H R2 or R1 C N R3 127 R2 Some Derivatives of Carboxylic Acids Amides are also named as derivatives of carboxylic acids. The suffix -amide is substituted for -ic acid or -oic acid. O O H3C C N C NH2 H H ethanamide or acetamide benzamide 128 Some Derivatives of Carboxylic Acids When an aryl or alkyl substituent is present on the N atom, the letter N and the name of the substituent are prefixed to the name of the unsubstituted amide. H2C O O H3C C N C N CH3 CH3 CH3 H N-ethylethanamide or N-ethylacetamide N-ethyl-N-methylbenzamide 129 Some Derivatives of Carboxylic Acids Acetaminophen – “Tylenol” - is an amide. O C HN CH 3 OH H H C H H acetaminophen 130 Summary of the Functional Groups A summary of the functional groups is: 131 132 Substitution Reactions In a substitution reaction an atom or group of atoms attached to a carbon atom is replaced (substituted for) by another atom or group of atoms. There is no change in the degree of saturation at the reactive carbon atom. Halogenation reactions are an important class of substitution reactions. Chlorine reacts with alkanes in free radical chain reactions (also substitution reactions). 133 Substitution Reactions Free radical chain reactions The halogenation of methane is one example. ·· ·· ·· Cl ·· Cl ·· ·· ·· heat or uv light ·· . · 2 · Cl ·· free radicals 134 Substitution Reactions ·· ·· ·· Cl ·· Cl ·· ·· ·· H ·· · H · C ·· H ·· H heat or uv light + ·· 2 ·· Cl . ·· free radicals ·· . ·· Cl ·· H ·· . · H ·C + ·· H methyl radical ·· ·· Cl ·· H ·· 135 Substitution Reactions heat or uv light ·· ·· ·· Cl ·· Cl ·· ·· ·· H ·· · H · C ·· H ·· H H ·· H ·· C . ·· H + + ·· 2 ·· Cl . ·· free radicals ·· . ·· Cl ·· ·· ·· ·· Cl ·· Cl ·· ·· ·· H ·· . · H ·C + ·· H methyl radical ·· ·· Cl ·· H ·· H ·· ·· H ·· C ·· Cl ·· ·· ·· H methyl chloride + ·· . ·· Cl ·· 136 Substitution Reactions Free radical chain reactions Many substitution reactions of alkanes produce more than one product. H H C Cl H H + Cl Cl Cl C Cl + HCl H 137 Substitution Reactions H H C Cl H + Cl Cl Cl H C Cl H + HCl H H Cl C Cl H + Cl Cl Cl C Cl + HCl Cl 138 Substitution Reactions H H C H Cl + Cl Cl Cl H Cl C Cl Cl + Cl Cl Cl C Cl H Cl Cl HCl H H C + H H Cl C Cl + Cl Cl Cl C Cl + HCl Cl + HCl Cl 139 Substitution Reactions Nitration reaction of an aromatic hydrocarbon replaces an H atom attached to an aromatic ring with a nitro, -NO2, group. NO + HNO 2 H2SO4 2 140 Addition Reactions An addition reaction involves an increase in the number of groups attached to carbon. The degree of saturation of the molecule is increased. H + C C H H H H H Cl 2 H C C H Cl Cl 141 Addition Reactions Hydrogenation is a very important kind of addition reaction. Hydrogenation is used to convert unsaturated fats and oils to saturated fats or oils. H + C C H H H H H H 2 H C C H H H 142 Elimination Reactions An elimination reaction involves the removal of groups attached to carbon. The degree of unsaturation increases. Br Br HC CH CH3 H3C Zn in H H C C CH3 H + C C acetic acid H C CH3 H H3C 3 or ethanol mixture of cis & trans-2-butene + ZnBr 143 2 Elimination Reactions Dehydration is an important kind of elimination reaction. H OH H H concentrated HC CH C C H H SO4 H H H 2 + H2O 144 Polymerization Reactions A polymer is a large molecule that consists of a high-molecular weight chain of small molecules. The small molecules that have been joined to form the polymer are called monomers. Synthetic polymers are a relatively new class of molecules. The first one, bakelite, was discovered in 1909. Nylon, which is still extensively used, was discovered in 1930’s. 145 Polymerization Reactions Addition polymerization is a large commercial process in the United States. Polyethylene is the addition polymer made in the largest quantities in the United States. Polyethylene is used to make Coke bottles, plastic bags, etc. 146 Polymerization Reactions Addition polymerization Polyethylene formation n H2C CH2 ethylene catalyst * CH2 CH2 n * polyethylene 147 Polymerization Reactions Addition polymerization Teflon is the material used in nonstick frying pans and other kitchen utensils. F F n C C F F catalyst heat tetrafluoroethylene * F F C C n * F F polytetrafluoroethylene or Teflon 148 Polymerization Reactions Formation of rubber Natural rubber is a polymer made of isoprene (2-methyl1,3-butadiene) units that form a unique stereoisomeric structure. CH3 CH3 H H3C H 2 C C 2n CH2 n * C C C CH2 CH CH2 CH * CH2 H2C isoprene natural rubber 149 Polymerization Reactions Vulcanization of rubber Natural rubber is a sticky, soft compound when heated which limited its commercial potential. Charles Goodyear discovered in 1839 that heating rubber with sulfur removed the stickiness and made the substance elastic. This is the basis of modern tire production. Vulcanization provides disulfide cross-linking bonds between the isoprene units. 150 Polymerization Reactions Copolymers If two different monomers are mixed and the polymerized, copolymers are formed. Styrene butadiene rubber - SBR - is an important copolymer used in tire production. 151 Polymerization Reactions Copolymers H H H 3 H H C C C C H H butadiene C C H + H styrene 152 Polymerization Reactions H * H C CH2 C H2C H CH2 C H2 C C C C H2 CH2 H H CH2 C C n * H H Styrene - butadiene rubber (SBR) 153 Polymerization Reactions Condensation Polymers Condensation polymers occur when two molecules react and eliminate a small molecule. Molecules eliminated commonly are water and HCl. Important condensation polymers include nylon, dacron, and kevlar. Dacron is used in clothing to make it wrinkle free. Blood does not clot in contact with dacron thus it is used in artificial arteries. 154 Polymerization Reactions Condensation Polymers Dacron formation HO H2 H2 C C OH HO + O ethylene glycol C O OH terephthalic acid 155 Polymerization Reactions O O H O C C O H2 H2 C C OC C O H2 H2 n H + H2O Dacron is a polyester 156 Polymerization Reactions Condensation Polymers Nylon was first made by Wallace Carothers in the 1930’s. Nylon is widely used in a variety of commercial products including stockings, rope, guitar strings, fire-proof clothing. 157 Polymerization Reactions Condensation Polymers Nylon 66 formation O HO C C H2 H2 C C H2 adipic acid H2 C C O OH + H2N H2 C C H2 H2 C C H2 H2 C C H2 NH2 hexamethylene diamine 158 Polymerization Reactions O H2N C C H2 H2 C C H2 H2 C C O H N C H2 H2 C C H2 H2 C C H2 H2 C O N H C n OH + H2O Nylon is a polyamide 159 Synthesis Question TNT, the explosive ingredient in dynamite, has the correct name of 2,4,6-trinitrotoluene. Draw the structure of TNT. 160 Synthesis Question CH3 O N 2 NO NO 2 2 TNT or 2,4,6-trinitrotoluene 161 Group Question Aerobic respiration produces carbon dioxide and water as its end products. Anaerobic respiration has different end products. What are the end products of anaerobic respiration? How could you easily detect that someone has switched from aerobic to anaerobic respiration? 162 End of Chapter 27 There are more organic compounds than any other type of chemical species. 163