ORGANIC CHEMISTRY Naming Saturated Hydrocarbons • The International Union of Pure and Applied Chemistry (IUPAC) names for the first 12 "straight-chain" or "normal" alkanes are: Number of Carbons in chain Prefix C-C C=C C C 1 Meth- Methane 2 Eth- Ethane Ethene Ethyne 3 Prop- Propane Propene Propyne 4 But- Butane Butene Butyne 5 Pent- Pentane Pentene Pentyne 6 Hex- Hexane Hexene Hexyne 7 Hept- Heptane Heptene Heptyne 8 Oct- Octane Octene Octyne 9 Non- Nonane Nonene Nonyne 10 Dec- Decane Decene Decyne 11 Undec- Undecane Undecene Undecyne 12 Dodec- Dodecane Dodecene Dodecyne 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 H C H H H C H H H or CH4 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 C H H C2H6 H H H H H C C C H H H C3H8 H 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. • Branched-chain alkanes are named by the following rules. H H H H H C C C C H H H H H H H H H C C C H H H H C H H n-butane 2-methylpropane Naming Saturated Hydrocarbons 1. 2 3 4 5 6 Choose the longest continuous chain of carbon atoms which gives the basic name or stem. 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. 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. The combined substituent numbers and names serve as a prefix for the basic hydrocarbon name. Separate numbers from numbers by commas and numbers from words by hyphens. Words are "run together". 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. • Three alkanes have the formula C5H12. – There are three structural isomers of pentane. CH3 H2 H2 CH3 C C C CH CH3 H3C C CH3 H3C CH3 H3C C H2 CH3 H2 n-pentane 2-methylbutane 2,2-dimethylpropane 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 •The number of structural isomers increases rapidly with increasing numbers of carbon atoms. •The boiling points of the alkanes increase with molecular weight. Alkanes and Cycloalkanes • Cyclic saturated hydrocarbons are called cycloalkanes. – They have the general formula CnH2n. • Some examples are: H2 C H 2C H2C CH 2 CH 2 H2 C H2C H2C cyclopentane CH 2 C H2 H2 H2 C C CH 2 cyclohexane H2C H2C H2C CH 2 CH 2 CH 2 cyclooctane Alkenes • 1. 2. 3. • The three classes of unsaturated hydrocarbons are: alkenes and cycloalkenes, CnH2n alkynes and cycloalkynes, CnH2n-2 aromatic hydrocarbons 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 – and propene, C3H6 H C C H H H • Each doubly bonded C atom is sp2 hybridized. • The sp2 hybrid consists of: – two s bonds (single bonds) and – one s and one p bond (double bond) C H C H H C H 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. • Polyenes contain two or more double H H bonds per molecule. H H H H • Indicate the number of double bondsH C C C C C H H C C C C C C C H with suffixes: H H H H H H H – -adiene for two double bonds. 1,3,5-hexatriene 1,3-hexadiene – -atriene for three double bonds, H etc. H H C H H • The positions of the substituents are H C C C C C C H indicated as for alkanes. H H H C H • The position of the C=C bond(s) H is/are given the lowest number(s) 2,3-dimethyl-1,3,5-hexatriene possible. H Cycloalkenes • Cycloalkenes have the general formula CnH2n-2. • Examples are: • cyclopentene • cyclohexene H H H C C C H H C C H H H H H H C C C H C H C H C H H H H 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 bonds. – The carbon atom will have one single bond and one triple bond. • 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 3-heptyne H H H C H C C H H H H H C C C C C H H H H H 2-octyne H Hydrocarbons: A Summary Carbon Atom Hybridization C uses C forms Example sp3 tetrahedral 4 sp3 hybrids 4 bonds CH4 sp2 trigonal planar 3 sp2 hybrids & 1p orbital 3 bonds 1 bond C2H4 sp linear 2 sp hybrids & 2 p orbitals 2 bonds 2 bonds C2H2 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. H H • The structure of benzene, C6H6, is: H C C C C C C H H H • Coal tar is the common source of benzene and many other aromatic compounds. H H • Some aromatic hydrocarbons that H H C C C C C contain fused rings are: • napthalene C C C H C C H H H Resonance in Benzene • C–C single bond = 154 pm • C=C bond = 134 pm • CC bonds in benzene = 139 pm • C6H6 has two resonance structures with alternating double bonds. • The π electrons are delocalized over the ring. H H H H C H C H C H H H C C C C C C HC C H CH H C CH C H Resonance structures of benzene, C6 H6 HC C H CH Abbreviated representation of resonance structures π electrons delocalized 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 CH 3 CH 3 CH 3 CH 3 CH 3 m-xylene CH 3 o-xylene p-xylene 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 • 1,2-dichloroethane, ClCH2CH2Cl Cl Cl H Cl C H C C H H Cl Cl • para-dichlorobenzene Cl Cl H 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. • 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. Alcohols and Phenols • Ethyl alcohol (ethanol), C2H5OH, is the most familiar alcohol. H H H C C H H OH • Phenol, C6H5OH, is the most familiar phenol. OH Alcohols and Phenols • 1. 2. • 3. • Alcohols can be classified into three classes: Primary (1°) alcohols like ethanol have the -OH group attached to a C atom that has one bond to another C atom. Secondary(2°) alcohols have the –OH group attached to a C atom that has bonds to 2 other C atoms. For example,2-propanol: 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 H3C C OH H2 H3C HC OH H3C OH H3C C CH3 CH3 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 H2 C OH C H2 H2 C OH CH3 1-pentanol 1-pentyl alcohol C H3C H C H2 H2 C CH3 2-pentanol 2-pentyl alcohol H2 H2 C H C H3C C CH3 OH 3-pentanol 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. OH H2 C HO H2 C C H2 CH CH3 H3C CH 3 1-butanol 2-butanol OH HO CH 2 CH H3C CH 2 CH 3 2-methyl-1-propanol H3C C CH 3 CH 3 2-methyl-2-propanol Alcohols and Phenols • There are eight isomeric five-carbon alcohols. HO C H2 H2 C C H2 H2 C OH CH3 1-pentanol C H3C H C H2 2-methyl-1-butanol C H3C H C H2 H2 C H3C C CH2 OH CH3 2-methyl-2-butanol 2 3-methyl-1-butanol H3C C 3-pentanol CH3 CH3H OH H2 H2 C H C CH3 C H3C OH CH3 CH3 C C C H H2 H2 CH3 CH3 2-pentanol CH3 HO H2 C C CH3 OH 2,2-dimethyl-1-propanol C H CH3 H3C H C OH 3-methyl-2-butanol 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 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 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 H3C H water O H H3C an alcohol O CH3 an ether • 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 ethylmethyl ether H3C O CH3 dimethyl ether H2 C H3C O H2 C diethyl ether CH3 Aldehydes and Ketones • The functional group in aldehydes and ketones is the carbonyl group. O R1 R2 or H carbonyl group Aldehydes and Ketones • Except for formaldehyde, aldehydes have one H atom and one organic group bonded to a carbonyl group. O H3C O O H ethanal or acetaldehyde H H methanal or formaldehyde H 3C C H2 H propanal or propionaldehyde • Ketones have two organic groups bonded to a carbonyl group. H3C O O O C C C CH 3 propanone or acetone H2C CH 3 CH 3 2-butanone or ethylmethylketone H 2C CH 3 CH 2 CH 3 3-pentanone or diethylketone 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 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 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 Carboxylic Acids O • Carboxylic acids contain the carboxyl functional group. C OH O • The general formula for carboxylic acids is: – R represents an alkyl or an aryl group C R1 OH • 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. Carboxylic Acids O O C C H H3C OH methanoic acid or formic acid ethanoic acid or acetic acid O O H3C H2 C C C H2 OH OH propanoic acid or propionic acid H3C C C H2 OH butanoic acid or butyric acid 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. 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 Nomenclature of Carboxylic Acids • Dicarboxylic acids contain two carboxyl groups per molecule. O OH C C HO O oxalic acid HO O O O C C C C H2 OH malonic acid HO C H2 H2 C C O succinic acid OH 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. HO HO O benzoic acid HO O O Cl p-chlorobenzoic acid OH O OH CH3 p-toluic acid O phthalic acid 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 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. • Common names are used for most ethers. • • 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. • • 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. • • • • Ethers Aldehydes and Ketones 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. 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. When compounds contain more than one functional group, the order of precedence determines which groups are named with prefix or suffix forms. The highest precedence group takes the suffix, with all others taking the prefix form. However, double and triple bonds only take suffix form (-en and -yn) and are used with other suffixes. Functional group Formula Prefix Suffix 1 Cations e.g. Ammonium –NH4+ -onioammonio- -onium -ammonium 2 Carboxylic acids –COOH carboxy- -oic acid* 3 Carboxylic acid derivatives Esters Acyl chlorides Amides –COOR –COCl –CONH2 R-oxycarbonylchloroformylcarbamoyl- -oyl chloride* -amide* 4 Nitrites Isocyanides –CN –NC cyanoisocyano- -nitrile* isocyanide 5 Aldehydes Thioaldehydes –CHO –CHS formylthioformyl- -al* -thial* 6 Ketones Thioketones >CO >CS oxothiono- -one -thione 7 Alcohols Thiols –OH –SH hydroxysulfanyl- -ol -thiol 8 Amines –NH2 amino- -amine 9 Ethers Thioethers –O– –S– -oxy-thio- Priority Isomerism • Isomers have identical composition but different structures • Two forms of isomerism – Constitutional (or structural) – Stereoisomerism • Constitutional – Same empirical formula but different atom-to-atom connections • Stereoisomerism – Same atom-to-atom connections but different arrangement in space. • Geometric - Geometric isomers can occur when there is a C=C double bond. • Optical - Optical isomers are molecules with non-superimposable mirror images. Such molecules are called CHIRAL. Pairs of chiral molecules are enantiomers. Chiral molecules in solution can rotate the plane of plane polarized light. Structural Isomers Stereoisomers: Geometric Geometric isomers can occur when there is a C=C double bond. Cis-2-butene Trans-2-butene Stereoisomers: Optical • Optical isomers are molecules with non-superimposable mirror images. • Such molecules are called CHIRAL • Pairs of chiral molecules are enantiomers. • Chiral molecules in solution can rotate the plane of plane polarized light. • Chirality generally occurs when a C atom has 4 different groups attached. Lactic acid Chirality: Handedness in Nature These molecules are non-superimposable mirror images. Sugars: Related to Alcohols • Sugars are carbohydrates, compounds with the formula Cx(H2O)y. CHO H OH 4 HO HO 5 3 H H OH 2 H 3 H OH 4 H OH 5 H HO 2 HO 1 OH OH -D-glucose H 1 CH2OH H OH 4 HO HO 5 HO 1 3 H H 2 OH H OH -D-glucose Open chain form What is the difference between a and b D-glucose? Glycosidic bonds: The anomeric hydroxyl group (axial) and a hydroxyl group of another sugar or some other compound can join together, splitting out water to form a glycosidic bond. R-OH + HO-R' --> R-O-R' + H2O Carbohydrates (also referred to as glycans) have the basic composition: Monosaccharides - simple sugars, with multiple hydroxyl groups. Based on the number of carbons (e.g., 3, 4, 5, or 6) a monosaccharide is a triose, tetrose, pentose, or hexose, etc. Disaccharides - two monosaccharides covalently linked Oligosaccharides - a few monosaccharides covalently linked. Polysaccharides - polymers consisting of chains of monosaccharide or disaccharide units Aldoses (e.g., glucose) have an aldehyde at one end. Ketoses (e.g., fructose) have a keto group, usually at C #2. Nomenclature for stereoisomers: D and L designations are based on the configuration about the single asymmetric carbon in glyceraldehyde. For sugars with more than one chiral center, the D or L designation refers to the asymmetric carbon farthest from the aldehyde or keto group. Most naturally occurring sugars are D isomers. D & L sugars are mirror images of one another. They have the same name. For example, D-glucose and L-glucose are shown at right. Haworth projections represent the cyclic sugars as having essentially planar rings, with the OH at the anomeric C1 extending either: •below the ring (a) •above the ring (b). Sucrose and Ribose H OH HO HO HO H OH O H OH O HO H H H CH2OH -D-Glucose H HO O OH Fructose H OH H H H Deoxyribose, the sugar in the DNA backbone. H CH2 OH Sucrose, common table sugar, has a glycosidic bond linking the anomeric hydroxyls of glucose and fructose. Because the configuration at the anomeric carbon of glucose is (O points down from the ring), the linkage is designated a(12). The full name is -Dglucopyranosyl-(12)b-D- fructopyranose. Fats and Oils H2 C HC H2 C O O CR O O CR O O CR What is the functional group in a fat or oil? R = organic group with NO C=C bonds C12 = Lauric acid C16 = Palmitic acid C18 = Stearic acid R = organic group with C=C bonds C18 = oleic acid H2 C HC H2 C O O CR O O CR O O CR Fats and Oils Fats with C=C bonds are usually LIQUDS Oleic acid: a monounsaturated fatty acid C=C bond Trans Fatty Acids •Oleic acid is a mono–unsaturated cisfatty acid •Trans fatty acids have deleterious health effects. •Trans fatty acids raise plasma LDL cholesterol and lower HDL levels. C=C bond Alpha-Amino Acids H2N H O C C OH R Amine H Alanine H3C C Chiral -carbon NH3 CO2 Acid Peptides and Proteins O H 3N OŠH CH3 Alanine HOCH 2 H 3N + H OŠ- O Serine peptide bond – H2O H HOCH2 H H 3N O N H O O Š CH3 Adding more peptide links ---> PROTEIN Polymers • Giant molecules made by joining many small molecules called monomers • Average production is 150 kg per person annually in the U.S. Polymer Classifications • Thermoplastics (polyethylene) soften and flow when heated • Thermosetting plastics — soft initially but set to solid when heated. Cannot be resoftened. • Other classification: plastics, fibers, elastomers, coatings, adhesives National Liner is a premium cured-in-place pipe trenchless rehabilitation system designed to repair sanitary and stormwater pipelines ranging from to 120 in. in diameter. Made of non-woven, needled polyester felt and saturated with a thermosetting resin, the liner is inserted into an upstream manhole and expanded with a hydrostatic head of water to press the liner tightly against the interior of the host pipe. Once in place, the liner is heated to activate the resin system, causing the resin to cure, and form a new structural pipe within the host pipe. National Envirotech Group Houston,TX Tel:800-547-1235 Web:www.nationalliner.com Polymer Preparation • Addition polymers — directly adding monomer units together • Condensation polymers — combining monomer units and splitting out a small water (water) Types of Polyethylene Linear, high density PE (HDPE) Branched, low density PE, LDPE Cross-linked PE, CLPE Types of Polyethylene Polymers based on Substituted Ethylenes, CH2=CHX CH2CH OH CH2CH n polyvinyl alcohol CH2CH OCCH3 n O polyvinyl acetate n polystyrene Table 11.12: others are PVC, acrylonitrile, polypropylene, polymethyl methacrylate Bubble Gum! A copolymer Styrene + butadiene Condensation Polymers O n HOC O COH + n HOCH2CH2OH terephthalic acid O C ethylene glycol O COCH2CH2O + H2 O n Polyethylene terephthalate (PET), a polyester Polyamides: Nylon •Each monomer has 6 C atoms in its chain. •A polyamide link forms on elmination of HCl •Result = nylon 66 •Proteins are polyamides