Chemistry: A Molecular Approach, 1st Ed. Nivaldo Tro Chapter 20 Organic Chemistry Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA 2008, Prentice Hall Structure Determines Properties • Organic compounds all contain carbon CO, CO2 , carbonates and carbides are inorganic other common elements are H, O, N, (P, S) • Carbon has versatile bonding patterns chains, rings, multiple bonds chain length nearly limitless • Carbon compounds generally covalent molecular; gases, liquids, or low melting solids; varying solubilities; nonconductive in liquid • C - C bonds unreactive (very stable) Tro, Chemistry: A Molecular Approach 2 Bond Energies and Reactivities C-C S-S Si-Si N-N O-O 347 kJ H3C-CH3 NONREACTIVE IN AIR 214 kJ 213 kJ 159 kJ 138 kJ EXTREMELY REACTIVE Tro, Chemistry: A Molecular Approach HS-SH SPONTANEOUS 3 BURNS IN AIR H3Si-SiH H2N-NH2 EXTREMELY REACTIVE HO-OH REACTIVE 3 Allotropes of Carbon - Diamond Tro, Chemistry: A Molecular Approach 4 Allotropes of Carbon - Graphite Tro, Chemistry: A Molecular Approach 5 Carbon Bonding • mainly forms covalent bonds • C is most stable when it has 4 single covalent bonds, but does form double and triple bonds C=C and C≡C are more reactive than C−C C with 4 single bonds is tetrahedral, 2 singles and 1 double is trigonal planar 2 doubles or 1 triple and 1 single is linear Tro, Chemistry: A Molecular Approach 6 Hydrocarbons • hydrocarbons contain only C and H aliphatic or aromatic • insoluble in water no polar bonds to attract water molecules • aliphatic hydrocarbons saturated or unsaturated aliphatics saturated = alkanes, unsaturated = alkenes or alkynes may be chains or rings chains may be straight or branched • aromatic hydrocarbons Tro, Chemistry: A Molecular Approach 7 Uses of Hydrocarbons Number of C atoms 1-4 5-7 6-18 12-24 18-50 50+ State Major Uses heating and cooking fuel liquids, solvents, (low boiling) gasoline gas liquids gasoline jet fuel; camp liquids stove fuel diesel fuel, liquids, lubricants, (high boiling) heating oil petroleum jelly, solids paraffin wax 8 Saturated Hydrocarbons • a saturated hydrocarbon has all C-C single bonds it is saturated with hydrogens • saturated aliphatic hydrocarbons are called alkanes • chain alkanes have the general formula CnH2n+2 Tro, Chemistry: A Molecular Approach 9 Unsaturated Hydrocarbons • unsaturated hydrocarbons have one of more C=C • double bonds or CC triple bonds unsaturated aliphatic hydrocarbons that contain C=C are called alkenes the general formula of a monounsaturated chain alkene is CnH2n remove 2 more H for each additional unsaturation • unsaturated aliphatic hydrocarbons that contain CC are called alkynes the general formula of a monounsaturated chain alkyne is CnH2n-2 remove 4 more H for each additional unsaturation Tro, Chemistry: A Molecular Approach 10 Unsaturated Hydrocarbons H3C H C CH3 C H CH3 H3C C C CH3 HC H2C CH3 H3C C C CH3 H2C H2C H2 C C CH2 H2C Tro, Chemistry: A Molecular Approach C H2 H C C H2 H2 C C H2 C CH2 C H2 H2C C H2 CH2 H2 C CH2 CH2 11 Aromatic Hydrocarbons • contain benzene ring structure • even though they are often drawn with C=C, they do not behave like alkenes Tro, Chemistry: A Molecular Approach 12 H2 C C H2C CH 3 H3C C C CH 3 H H2C CH CH3 C C 3 C H3C H3C C CH2 H H C 2 CH 3 C H2 H2 C C H C C H2 H2 C CH22 HC CH H2C H H22C CH2 C CH C 2 C H2 H2 alkanes alkenes alkynes Tro, Chemistry: A Molecular Approach 13 Tro, Chemistry: A Molecular Approach 14 Formulas • molecular formulas just tell you what • • kinds of atoms are in the molecule, but they don’t tell you how they are attached structural formulas show you the attachment pattern in the molecule models not only show you the attachment pattern, but give you an idea about the shape of the molecule 15 Condensed Structural Formulas • attached atoms listed in order central atom with attached atoms • follow normal bonding patterns use to determine position of multiple bonds • () used to indicate more than 1 identical group attached to same previous central atom unless () group listed first in which case attached to next central atom Tro, Chemistry: A Molecular Approach 16 Line-Angle Formulas • each angle, and beginning and end represent a C atom • H omitted on C included on functional groups • multiple bonds indicated double line is double bond, triple line is triple bond Tro, Chemistry: A Molecular Approach 17 Formulas Tro, Chemistry: A Molecular Approach 18 Formulas H H CH4 C H H C2H6 C3H8 C4H10 C4H10 CH3CH3 CH3CH2CH3 CH3CH2CH2CH3 C(CH3)2 H H H H H H C C H H H H H C C C H H H H H H H C C C C H H H H H H H C C C C H H H H Tro, Chemistry: A Molecular Approach H H H H H 19 Isomerism • Isomers = different molecules with the same • molecular formula Structural Isomers = different pattern of atom attachment Constitutional Isomers • Stereoisomers = same atom attachments, different spatial orientation Tro, Chemistry: A Molecular Approach 20 H H H H H H C C C C H H C C C Structural Isomers of C4H10 H HButane, HH HHBPH= 0°C C C C H H H CH C C C H H H H H H H H H H H H H HIsobutane, H HH BP H = -12°C H C H C C C H HH H H C C HC H H H H H H C H H C H H Tro, Chemistry: A Molecular Approach H H 21 Rotation about a bond is not isomerism Tro, Chemistry: A Molecular Approach 22 Possible Structural Isomers Carbon Molecular Possible Content Formula Isomers 4 C4H10 2 5 C5H12 3 6 C6H14 5 7 C7H16 9 8 C8H18 18 9 C9H20 35 10 C10H22 75 Tro, Chemistry: A Molecular Approach 23 Ex 20.1 – Write the structural formula and carbon skeleton formula for C6H14 start by connecting the carbons in a line C C C C CC CC C C CC C C C C C C C C C C C determine the C skeleton of the other isomers Tro, Chemistry: A Molecular Approach 24 Ex 20.1 – Write the structural formula and carbon skeleton formula for C6H14 H fill in the H to give each C 4 bonds H H H H H C C C C C C H C C H H H H H C H C H C H C C H C C H H H H H H C C C C H C C H H H C H H C H H H H H H H C H H H H H H H H C H C H CC C C H C H C H H H H H H C C C H H H H H H H H C CC C C CC C C C H H H C H H C H H H H Ex 20.1 – Write the structural formula and carbon skeleton formula for C6H14 convert each to a carbon skeleton formula – each bend and the ends represent C atoms H H H H H H H C C C C C C H H H H H H H H H H H H C H H H C C C H H H H H H H H C C H H C C H H H H H H C C C C C H H H H C H H H H H H H C C C H C H H H H H H H H H H H C C C C H H H C H H C H H H H Stereoisomers • stereoisomers are different molecules whose atoms are connected in the same order, but have a different spatial direction • optical isomers are molecules that are nonsuperimposable mirror images of each other • geometric isomers are stereoisomers that are not optical isomers Tro, Chemistry: A Molecular Approach 27 Nonsuperimposable Mirror Images mirror image cannot be rotated so all its atoms align with the same atoms of the original molecule Tro, Chemistry: A Molecular Approach 28 Chirality • any molecule with a nonsuperimposable mirror image is said to be chiral • any carbon with 4 different substituents will be a chiral center • a pair of nonsuperimposable mirror images are called a pair of enantiomers Tro, Chemistry: A Molecular Approach 29 Optical Isomers of 3-methylhexane Tro, Chemistry: A Molecular Approach 30 Plane Polarized Light • light that has been filtered so that only those waves traveling in a single plane are allowed through Tro, Chemistry: A Molecular Approach 31 Optical Activity • a pair of enantiomers have all the same physical properties except one – the direction they rotate the plane of plane polarized light each will rotate the plane the same amount, but in opposite directions dextrorotatory = rotate to the right levorotatory = rotate to the left • an equimolar mixture of the pair is called a racemic mixture rotations cancel, so no net rotation Tro, Chemistry: A Molecular Approach 32 Chemical Behavior of Enantiomers • a pair of enantiomers will have the same chemical reactivity in a non-chiral environment • but in a chiral environment they may exhibit different behaviors enzyme selection of one enantiomer of a pair Tro, Chemistry: A Molecular Approach 33 • • • • • Alkanes aka paraffins aliphatic general formula CnH2n+2 for chains very unreactive come in chains or/and rings CH3 groups at ends of chains, CH2 groups in the middle chains may be straight or branched • saturated • branched or unbranched Tro, Chemistry: A Molecular Approach 34 Name Lewis Structure H Methane H C H Ethane Propane H H Pentane Hexane H H H H H H C C H H C H Butane Formula H CH4 Boiling Point -162°C CH3CH3 -89°C CH3CH2CH3 -42°C CH3CH2CH2CH3 0°C CH3CH2CH2CH2CH3 36°C CH3CH2CH2CH2CH2CH3 69°C H H H C C H H H H H H H C C C C H H H H H H H H H H C C C C C H H H H H H H H H H H C C C C C C H H H H H H Tro, Chemistry: A Molecular Approach H H 35 Naming • each name consists of 3 parts prefix indicates position, number, and type of branches indicates position, number, and type of each functional group parent indicates the length of the longest carbon chain or ring suffix indicates the type of hydrocarbon – ane, ene, yne certain functional groups Tro, Chemistry: A Molecular Approach 36 Naming Alkanes 1) Find the longest continuous carbon chain 2) Number the chain from end closest to a branch if first branches equal distance use next in 3) Name branches as alkyl groups locate each branch by preceding its name with the carbon number on the chain 4) List branches alphabetically do not count n-, sec-, t-, count iso 5) Use prefix if more than one of same group present di, tri, tetra, penta, hexa do not count in alphabetizing 37 Alkyl Groups H H C H CH3-, METHYL H H H C C H H CH3CH2-, ETHYL H H H H C C C H H H CH3CH2CH2-, PROPYL H CH3 H C C H H (CH3)2CH-, ISOPROPYL Tro, Chemistry: A Molecular Approach 38 More Alkyl Groups H H H H H C C C C H H H H CH3CH2CH2CH2-, n-BUTYL H H CH3 H C C C H H H CH3CH2(CH3)CH-, sec-BUTYL H H C H (CH3)2CHCH2-, ISOBUTYL CH3 H C C H H CH3 H 3C C CH3 Tro, Chemistry: A Molecular Approach (CH3)3C-, tert- BUTYL 39 Examples of Naming Alkanes 2-methylpentane 3-isopropyl-2,2-dimethylhexane H H H H H H H C C C C C H CH3 H H H H CH3 H H H H C C C C C H CH3 CH H H H C H H CH3 CH3 Tro, Chemistry: A Molecular Approach 40 Example – Name the alkane CH3CHCH2CHCH3 CH3 CH3 1) find the longest continuous C chain and use it to determine the base name CH3CHCH2CHCH3 CH3 CH3 since the longest chain has 5 C the base name is pentane Tro, Chemistry: A Molecular Approach 41 Example – Name the alkane CH3CHCH2CHCH3 CH3 CH3 2) identify the substituent branches CH3CHCH2CHCH3 CH3 CH3 there are 2 substituents both are 1 C chains, called methyl Tro, Chemistry: A Molecular Approach 42 Example – Name the alkane 3) number the chain from the end closest to a substituent branch if first substituents equidistant from end, go to next substituent in then assign numbers to each substituent based on the number of the main chain C it’s attached to 1 2 3 4 5 CH3CHCH2CHCH3 both substituents are equidistant from the end CH3 2 Tro, Chemistry: A Molecular Approach CH3 4 43 Example – Name the alkane 4) write the name in the following order 1) substituent number of first alphabetical substituent followed by dash 2) substituent name of first alphabetical substituent followed by dash if it’s the last substituent listed, no dash use prefixes to indicate multiple identical substituents 3) repeat for other substituents alphabetically 4) name of main chain CH3CHCH2CHCH3 CH3 2 2,4 – dimethylpentane CH3 4 Tro, Chemistry: A Molecular Approach 44 Practice – Name the Following CH3 CH3 CHCHCH2 CH3 CH2 CH3 Tro, Chemistry: A Molecular Approach 45 Practice – Name the Following CH3 CH3 CHCHCH2 CH3 CH2 CH3 3-ethyl-2-methylpentane Tro, Chemistry: A Molecular Approach 46 Drawing Structural Formulas • draw and number the • • base chain carbon skeleton add the carbon skeletons of each substituent on the appropriate main chain C add in required H’s 4-ethyl-2-methylhexane C C C C C C 1 2 3 4 5 6 C C C C C C C CH3 CH CH2 CH CH2 CH3 CH3 Tro, Chemistry: A Molecular Approach C C H2C CH3 47 Practice – Draw the structural formula of 4isopropyl-2-methylheptane Tro, Chemistry: A Molecular Approach 48 Practice – Draw the structural formula of 4isopropyl-2-methylheptane CH3 CH CH2 CH CH2 CH2 CH3 CH3 HC CH3 CH3 Tro, Chemistry: A Molecular Approach 49 Alkenes • also known as olefins • aliphatic, unsaturated C=C double bonds • formula for one double bond = CnH2n subtract 2 H from alkane for each double bond • trigonal shape around C flat • much more reactive than alkanes • polyunsaturated = many double bonds Tro, Chemistry: A Molecular Approach 50 Tro, Chemistry: A Molecular Approach 51 Alkenes ethene = ethylene H H propene H C C C C H H H Tro, Chemistry: A Molecular Approach H CH3 52 Physical Properties of Alkenes Molar Mass BP, °C Density, g/cm 3 28 -104 0.52 Name ethene Formula CH2=CH2 propene CH2=CHCH3 42 -47 0.59 1-butene CH2=CHCH2CH3 56 -6 0.59 1-pentene CH2=CH(CH2)2CH3 70 30 0.64 1-hexene CH2=CH(CH2)3CH3 84 64 0.68 1-heptene CH2=CH(CH2)4CH3 98 93 0.70 1-octene CH2=CH(CH2)5CH3 112 122 0.72 1-nonene CH2=CH(CH2)6CH3 126 146 0.73 1-decene CH2=CH(CH2)7CH3 140 171 0.74 Tro, Chemistry: A Molecular Approach 53 Alkynes • • • • also known as acetylenes aliphatic, unsaturated CC triple bond formula for one triple bond = CnH2n-2 subtract 4 H from alkane for each triple bond • linear shape • more reactive than alkenes Tro, Chemistry: A Molecular Approach 54 Tro, Chemistry: A Molecular Approach 55 Alkynes ethyne = acetylene H C C H Tro, Chemistry: A Molecular Approach propyne H C C CH3 56 Physical Properties of Alkynes Name Formula Molar Mass BP, °C Density, g/cm 3 ethyne CHCH 28 -104 0.52 propyne CHCCH3 42 -47 0.59 1-butyne CHCCH2CH3 56 -6 0.59 1-pentyne CHC(CH2)2CH3 70 30 0.64 1-hexyne CHC(CH2)3CH3 84 64 0.68 1-heptyne CHC(CH2)4CH3 98 93 0.70 1-octyne CHC(CH2)5CH3 112 122 0.72 1-nonyne CHC(CH2)6CH3 126 146 0.73 1-decyne CHC(CH2)7CH3 140 171 0.74 Tro, Chemistry: A Molecular Approach 57 Naming Alkenes and Alkynes • change suffix on main name from -ane to -ene for base name of alkene, or to -yne for the base name of the alkyne • number chain from end closest to multiple bond • number in front of main name indicates first carbon of multiple bond Tro, Chemistry: A Molecular Approach 58 Examples of Naming Alkenes 2-methyl-1-pentene H 3-isopropyl-2,2-dimethyl-3-hexene H H H H C C C C C H CH3 H H H H CH3 C C H CH3 CH C H H H C C C H H H H CH3 CH3 Tro, Chemistry: A Molecular Approach 59 Examples of Naming Alkynes 3-methyl-1-pentyne H 4-isopropyl-5,5-dimethyl-2-hexyne H C C H H H C C C CH3 H H H CH3 H C C H CH3 CH C H H C C C H H CH3 CH3 Tro, Chemistry: A Molecular Approach 60 Name the Alkene 1) find the longest, continuous C chain that contains the double bond and use it to determine the base name H2C CH3 H3C CH C CH CH3 H2C CH3 since the longest chain with the double bond has 6 C the base name is hexene Tro, Chemistry: A Molecular Approach 61 Name the Alkene 2) identify the substituent branches H2C CH3 H3C CH C CH CH3 H2C CH3 there are 2 substituents one is a 1 C chain, called methyl the other one is a 2 C chain, called ethyl Tro, Chemistry: A Molecular Approach 62 Name the Alkene 3) number the chain from the end closest to the double bond then assign numbers to each substituent based on the number of the main chain C it’s attached to 3 H2C CH3 4 H3C CH C CH CH3 4 3 2 1 H2C CH3 5 Tro, Chemistry: A Molecular Approach 6 63 Name the Alkene 4) write the name in the following order 1) substituent number of first alphabetical substituent – substituent name of first alphabetical substituent – use prefixes to indicate multiple identical substituents 2) repeat for other substituents 3) number of first C in double bond – name of main chain 3 H2C CH3 4 H3C CH 3–ethyl– 4–methyl–2–hexene C CH CH3 4 3 2 1 H2C CH3 5 6 Tro, Chemistry: A Molecular Approach 64 Practice – Name the Following CH3 H3C C C CH2 CH3 H2C CH3 Tro, Chemistry: A Molecular Approach 65 Practice – Name the Following CH3 H3C 3C C4 CH2 CH3 5 6 H2C CH3 2 1 3,4-dimethyl-3-hexene Tro, Chemistry: A Molecular Approach 66 Name the Alkyne 1) find the longest, continuous C chain that contains the triple bond and use it to determine the base name CH3 CH CH2 CH C CH3 C CH3 HC CH3 CH3 since the longest chain with the triple bond has 7 C the base name is heptyne Tro, Chemistry: A Molecular Approach 67 Name the Alkyne 2) identify the substituent branches CH3 CH CH2 CH C CH3 HC C CH3 CH3 CH3 there are 2 substituents one is a 1 C chain, called methyl the other one is called isopropyl Tro, Chemistry: A Molecular Approach 68 Name the Alkyne 3) number the chain from the end closest to the triple bond then assign numbers to each substituent based on the number of the main chain C it’s attached to CH3 CH CH2 CH C 7 6 5 4 3 6 CH3 HC 4 C 2 CH3 1 CH3 CH3 Tro, Chemistry: A Molecular Approach 69 Name the Alkyne 4) write the name in the following order 1) substituent number of first alphabetical substituent – substituent name of first alphabetical substituent – use prefixes to indicate multiple identical substituents 2) repeat for other substituents 3) number of first C in double bond – name of main chain CH3 CH CH2 CH C 7 6 5 4 3 6 CH3 HC 4 C 2 CH3 1 CH3 CH3 Tro, Chemistry: A Molecular Approach 4–isopropyl–6–methyl–2–heptyne 70 Practice – Name the Following CH3 H3C C C CH CH2CH3 Tro, Chemistry: A Molecular Approach 71 Practice – Name the Following CH3 H3C C C 3 2 CH 1 CH2CH3 4 5 3,3-dimethyl-1-pentyne Tro, Chemistry: A Molecular Approach 72 Geometric Isomerism • because the rotation around a double bond is highly • • • restricted, you will have different molecules if groups have different spatial orientation about the double bond this is often called cis-trans isomerism when groups on the doubly bonded carbons are cis, they are on the same side when groups on the doubly bonded carbons are trans, they are on opposite sides Tro, Chemistry: A Molecular Approach 73 Free Rotation Around C─C Tro, Chemistry: A Molecular Approach 74 Cis-Trans Isomerism Tro, Chemistry: A Molecular Approach 75 Reactions of Hydrocarbons • all hydrocarbons undergo combustion • combustion is always exothermic about 90% of U.S. energy generated by combustion 2 CH3CH2CH2CH3(g) + 13 O2(g) → 8 CO2(g) + 10 H2O(g) CH3CH=CHCH3(g) + 6 O2(g) → 4 CO2(g) + 4 H2O(g) 2 CH3CCCH3(g) + 11 O2(g) → 8 CO2(g) + 6 H2O(g) Tro, Chemistry: A Molecular Approach 76 Other Alkane Reactions • Substitution replace H with a halogen atom initiated by addition of energy in the form of heat or ultraviolet light to start breaking bonds generally get multiple products with multiple substitutions H H H C C H + Cl Cl H H Tro, Chemistry: A Molecular Approach heat or UV light H Cl H C C H + H Cl H H 77 Other Alkene and Alkyne Reactions • Addition reactions adding a molecule across the multiple bond • Hydrogenation = adding H2 converts unsaturated molecule to saturated alkene or alkyne + H2 → alkane • Halogenation = adding X2 • Hydrohalogenation = adding HX HX is polar when adding a polar reagent to a double or triple bond, the positive part attaches to the carbon with the most H’s 78 Addition Reactions HH CC HH C CC HCl + ++ H-Cl 22 CH CH333 CH Tro, Chemistry: A Molecular Approach HH HH Cl H H H CC HH HH CH CH 3 33 CC ClCl H 79 Aromatic Hydrocarbons • contain benzene ring structure • even though they are often drawn with C=C, they do not behave like alkenes Tro, Chemistry: A Molecular Approach 80 Resonance Hybrid • the true structure of benzene is a resonance hybrid of two structures Tro, Chemistry: A Molecular Approach 81 Naming Monosubstituted Benzene Derivatives • (name of substituent)benzene halogen substituent = change ending to “o” F CH2CH2CH3 propylbenzene fluorobenzene • or name of a common derivative CH3 NH2 toluene aniline Tro, Chemistry: A Molecular Approach OH phenol HC CH2 styrene 82 Naming Benzene as a Substituent • when the benzene ring is not the base name, it is called a phenyl group H2C CH CH2 CH CH2 CH3 4-phenyl-1-hexene Tro, Chemistry: A Molecular Approach 83 Naming Disubstituted Benzene Derivatives • number the ring starting at attachment for first substituent, then move toward second order substituents alphabetically use “di” if both substituents the same CH3 F 3 1 2 1 Br 1-bromo-3-fluorobenzene Tro, Chemistry: A Molecular Approach 2 CH3 1,2-dimethylbenzene 84 Naming Disubstituted Benzene Derivatives • alternatively, use relative position prefix ortho- = 1,2; meta- = 1,3; para- = 1,4 CH3 CH3 CH3 Cl Cl Cl 2-chlorotoluene ortho-chlorotoluene o-chlorotoluene Tro, Chemistry: A Molecular Approach 3-chlorotoluene meta-chlorotoluene m-chlorotoluene 4-chlorotoluene para-chlorotoluene p-chlorotoluene 85 Practice – Name the Following F Br Br Cl Tro, Chemistry: A Molecular Approach 86 Practice – Name the Following F Br Br Cl 1-chloro-4-fluorobenzene Tro, Chemistry: A Molecular Approach 1,3-dibromobenzene or meta-dibromobenzene or m-dibromobenzene 87 Polycyclic Aromatic Hydrocarbons • contain multiple benzene rings fused together fusing = sharing a common bond Tro, Chemistry: A Molecular Approach 88 Reactions of Aromatic Hydrocarbons • most commonly, aromatic hydrocarbons undergo substitution reactions – replacing H with another atom or group Tro, Chemistry: A Molecular Approach 89 Functional Groups • other organic compounds are hydrocarbons in which • functional groups have been substituted for hydrogens a functional group is a group of atoms that show a characteristic influence on the properties of the molecule generally, the reactions that a compound will perform are determined by what functional groups it has since the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol R R group Tro, Chemistry: A Molecular Approach CH3—OH functional group 90 91 Alcohols • R-OH • ethanol = CH3CH2OH grain alcohol = fermentation of sugars alcoholic beverages proof number = 2X percentage of alcohol gasohol • isopropyl alcohol = (CH3)2CHOH 2-propanol rubbing alcohol poisonous • methanol = CH3OH wood alcohol = thermolysis of wood paint solvent poisonous Tro, Chemistry: A Molecular Approach 92 Naming Alcohols • main chain contain OH • number main chain from end closest to OH • give base name ol ending and place number of C • on chain where OH attached in front name as hydroxy group if other higher precedence group present 1CH 2CH 3 2 OH CH3 3CH 4 C 5CH 6CH 2 CH2CH3 4-ethyl-4-methyl-3-hex-5-enol Tro, Chemistry: A Molecular Approach 93 Reactions of Alcohols Nucleophilic Substitution CH3 OH + HCl CH3Cl + H2O Acid Catalyzed Elimination (Dehydration) CH3 CH2OH CH2 CH2 + H2O H2SO4 Oxidation CH3 -2H CH2OH CH3 -2H CHO CH3 COOH with Reactive Metals CH3 OH Tro, Chemistry: A Molecular Approach + Na CH3O−Na+ + ½ H2 94 • • • • • • Aldehydes and Ketones contain the carbonyl group aldehydes = at least 1 side H ketones = both sides R groups many aldehydes and ketones have pleasant tastes and aromas some are pheromones formaldehyde = H2C=O pungent gas formalin = a preservative wood smoke, carcinogenic • acetone = CH3C(=O)CH3 O C formaldehyde acetone nail-polish remover Tro, Chemistry: A Molecular Approach 95 Aldehyde Odors and Flavors • butanal = butter O C CH2CH2CH3 H O • vanillin = vanilla HO O H HO • benzaldehyde = almonds O H C • cinnamaldehyde = cinnamon O H C C H C H 96 Ketone Odors and Flavors • acetophenone = pistachio O C H3C • carvone = spearmint H3C CH2 O C • ionone = raspberries CH3 H3C CH3 O H C C C CH3 H CH3 • muscone = musk O CH3 97 Reactions • aldehydes and ketones are generally synthesized by the oxidation of alcohols • therefore, reduction of an aldehyde or ketone results in an alcohol Tro, Chemistry: A Molecular Approach 98 Carbonyl Group C=O group is highly polar many reactions involve addition across C=O, with positive part attached to O Tro, Chemistry: A Molecular Approach 99 Addition to C=O Tro, Chemistry: A Molecular Approach 100 Carboxylic Acids • • • • RCOOH sour tasting weak acids citric acid O O CH2 C OH HO C C OH CH2 C OH O found in citrus fruit • ethanoic acid = acetic acid vinegar O CH3 C OH • methanoic acid = formic acid insect bites and stings Tro, Chemistry: A Molecular Approach O H C OH 101 Carboxylic Acids • made by the oxidation of aldehydes and alcohols OH on the end of the chain • always on main chain has highest precedence • C of group always C1 O C O H oxidation benzaldehyde OH H3C CH2 position not indicated in name ethanol C OH benzoic acid oxidation O H3C C OH ethanoic acid • change ending to oic acid Tro, Chemistry: A Molecular Approach 102 Naming Carboxylic Acids Tro, Chemistry: A Molecular Approach 103 Esters • R–COO–R • sweet odor • made by reacting carboxylic acid with an alcohol methyl butanoate RaCOOH + RbOH RaCOORb + H2O O • name alkyl group from alcohol, then C OH acid name with oate ending precedence over carbonyls, but not carboxylic acid number from end with ester group Tro, Chemistry: A Molecular Approach O C CH3 O aspirin 104 Naming Esters Tro, Chemistry: A Molecular Approach 105 Condensation Reactions • a condensation reaction is any organic reaction driven by the removal of a small molecule, like water • acid estersanhydrides are made by arethe made condensation by the condensation reaction reaction betweenbetween a carboxylic 2 carboxylic acid andacid an alcohol molecules + O R C OH the reaction is driven acid catalyzed by heat O HO C Tro, Chemistry: A Molecular Approach O R' R C O O C + R' HOH 106 Synthesis of Aspirin (Acetylsalicylic Acid) Tro, Chemistry: A Molecular Approach 107 Ethers • R– O – R • ether = diethyl ether = CH3CH2OCH2CH3 anesthetic • to name ethers, name each alkyl group attached to the O, then add the word ether to the end diethyl ether Tro, Chemistry: A Molecular Approach 108 Amines • • • • • N containing organic molecules very bad smelling form when proteins decompose organic bases name alkyl groups attached to the N, then add the word amine to the end NH2 H3C CH2 ethylamine H3C NH H3C CH2 ethylmethylamine Tro, Chemistry: A Molecular Approach H2NCH2CH2CH2CH2NH2 putrescine H2NCH2CH2CH2CH2CH2NH2 cadaverine 109 Amines • many amines are biologically active dopamine – a neurotransmitter epinephrine – an adrenal hormone pyridoxine – vitamin B6 HO CH2CH2NH2 HO dopamine • alkaloids are plant products that are alkaline and biologically active toxic coniine from hemlock cocaine from coca leaves nicotine from tobacco leaves mescaline from peyote cactus morphine from opium poppies Tro, Chemistry: A Molecular Approach N N CH3 nicotine 110 Amine Reactions • weak bases react with strong acids to form ammonium salts RNH2 + HCl → RNH3+Cl− • react with carboxylic acids in a condensation reaction to form amides RCOOH + HNHR’ RCONHR’ + H2O Tro, Chemistry: A Molecular Approach 111 Macromolecules • polymers are very large molecules made by repeated linking together of small molecules monomers • natural • modified natural polymers • synthetic plastics, elastomers (rubber), fabrics, adhesives • composites additives such as graphite, glass, metallic flakes Tro, Chemistry: A Molecular Approach 112 Natural Polymers • polysaccharides cellulose (cotton) starch • • • • • • proteins nucleic acids (DNA) natural latex rubber, etc. shellac amber, lignin, pine rosin asphalt, tar Tro, Chemistry: A Molecular Approach 113 Modified Natural Polymers • Cellulose Acetate Rayon film • Vulcanized Rubber • Gun Cotton • Celluloid ping-pong balls • Gutta Percha fill space for root canal • Casein buttons, mouldings, adhesives Tro, Chemistry: A Molecular Approach 114 Polymerization • the process of linking the monomer units together • two processes are addition polymerization and • condensation polymerization monomers may link head-to-tail, or head-to-head, or tail-to-tail head-to-tail most common regular pattern gives stronger attractions between chains than random arrangements Tro, Chemistry: A Molecular Approach 115 H H H H H C C C C Cl H Cl H Head-to-Tail Head Tail Head Tail H H H H H C C C C H Cl Cl Tail H Head Head Tail Head-to-Head, Tail-to-Tail 116 Addition Polymerization • monomers add to the growing chain in such a manner that all the atoms in the original monomer wind up in the chain no other side products formed, no atoms eliminated • first monomer must “open” to start reaction done with heat or addition of an initiator • chain reaction each added unit ready to add another Tro, Chemistry: A Molecular Approach 117 Addition Polymerization initiator H H C H etc. initiator C Cl H H C C Cl H H H H H C C C Cl H H H H H H C C C Cl H Cl • H C Cl H H H H + H C + H C Cl H C H H H H H C C C C Cl H Cl H • H H H H H H C C C C C C Cl H Cl H Cl H • Condensation Polymerization • monomer units are joined by removing small molecules from the combining units polyesters, polyamides lose water • no initiator needed • chain reaction • each monomer has two reactive ends, so chain can grow in two directions Tro, Chemistry: A Molecular Approach 119 Condensation Polymerization + HO HO + O O C C O O C C Tro, Chemistry: A Molecular Approach OH + HO O CH2 CH2 CH2 OH CH2 OH + H2O 120 Nylon • polyamides • good physical properties affected by moisture • • • • very good heat resistance excellent chemical resistance excellent wear resistance nylon 6,6 made by condensing 1,6–hexandiamine, H2N–(CH2)6–NH2, with hexandioic acid, HOOC–(CH2)4–COOH O O HN (CH2)6 NH Tro, Chemistry: A Molecular Approach C (CH2)4 C 121 Tro, Chemistry: A Molecular Approach 122