Power Point to Accompany Principles and Applications of Inorganic, Organic, and Biological Chemistry Denniston, Topping, and Caret 4th ed Chapter 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11-1 Organic Chemistry-History Historically - compounds from living systems (plants and animals) A “vital force”, ie. life was thought to be necessary to make organic chemicals. In 1828 Wohler synthesized urea from purely inorganic chemicals. Urea, found in urine, was definitely an organic compound! O KCNO + NH4Cl H2N C NH2+ KCl urea 11-2 Modern Organic Chemistry The Study of Carbon Compounds (some exceptions: for example carbonates, carbon dioxide, etc.) Biochemistry is now the field that studies chemicals of life. 11-3 Examples of Organic Chemicals Foods Carbohydrates Fats Proteins Clothing silk, linen, wool, cotton, Dacron, Nylon, Orlon, etc. Plastics Pharmaceuticals Detergents and Soaps Pesticides Gasoline and oils Water purification 11-4 11.1 Why is Carbon Unique? 1. Forms four covalent bonds 2. Bonds covalently to: H, O, N, P, S, and all other nonmetals (except noble gases) 3. Carbon atoms join to form: H2 a. Chains and b. Rings C CH3CH2CH2CH3 H2C CH2 H2C CH2 11-5 Why is carbon unique?: 2 4. Carbon can form H2C CH2 multiple bonds to H2C O itself, oxygen, and nitrogen. H2C NH double bonds HC CH HC N triple bonds 11-6 Why is Carbon Unique?: 3 4. Many carbon compounds exist in the form of isomers. Isomers are compounds with the same molecular formula but different structures. An isomer example: A, B, and C all are C4H10 but have different structures. See the next slide! 11-7 Why is Carbon Unique?: 3b Isomer Examples. All C4H8 CH3CH2CH CH2 A CH3CH CH CH3 B CH2 CH2 C CH2 CH2 11-8 Organic vs Inorganic: Differences Organic Inorganic Bonding Covalent Ionic Physical State (room temp) Gas/liquid common Solids common Melting points Tend to be low Tend to be very high Sol. In water Tend to be insoluble Much higher percent soluble Conductivity Nonconductors Conduct in soln. and molten 11-9 Families of Compounds: Hydrocarbons Hydrocarbons contain only carbon and hydrogen. They are nonpolar molecules and consequently are not soluble in water but are soluble in typical nonpolar organic solvents like toluene or pentane. Hydrocarbons are constructed of chains or rings of carbon atoms with sufficient hydrogens to fulfill carbons need for four bonds. 11-10 Hydrocarbons Aliphatics Aromatics Structures Based On: Chains and nonbenzenoid rings Benzene ring 11-11 Hydrocarbons Aliphatics Aromatics Alkanes and cycloalkanes Alkenes and cycloalkenes Alkynes and cycloalkynes 11-12 Functional groups CH3 CH3 ethane Alkanes are compounds that CH3 CH2 CH3 contain only propanecarbon-carbon and burned in a barbecue grill carbon-hydrogen CH2 CH2 single bonds. CH2 For example: CH2 CH2 CH2 cyclohexane-a ring alkane 11-13 Functional groups-2 alkenes have a carbon-carbon double bond H2C CH2 ethene: basis of polyethylene plastics H H C CH2 alkynes have a carbon-carbon triple bond CH3 CH2 H CH2 CH2 CH2 CH2 H C C CH2 C CH2 CH2 CH2 CH2 female silkworm moth OH sex attractant HC CH acetylene-welding gas in oxyacetylene torch 11-14 Functional groups-3 alcohols have the general formula: ROH (R is a carbon group) ethers have the general formulas: R-O-R, Ar-O-R, Ar-O-Ar Ar is also a carbon group but is “aromatic” phenols have the general formula: Ar-OH (aromatic only!) CH3CH2 OH ethanol, drinking alcohol CH3 CH2 O CH2 CH3 diethyl ether, a general anesthetic OH aromatic ring phenol-an early topical anesthetic 11-15 Functional groups-4 aldehydes have the O general formula R1 C H R1 may be H or any carbon group ketones have the O general formula R1 C R2 aldehyde carbonyl O 2H C CH CH2OPO3 OH glyceraldehyde-3-phosphate from glucose metabolism ketone carbonyl O O neither R1 nor R2 CH3C CH2 C O can be H acetoacetate ion, product of fat metabolism 11-16 Functional groups-5 acid groups carboxylic acids have the O general formula O CH2 C OH R1 C OH HO C CO2H condensed formula CH C OH 2 R1 may be carbon or H O esters have the general citric acid, found in fruits O formula O R1 C OR2 R1 may be carbon or H but R2 cannot be H or it would be an acid! ester carbonyl C O CH 3 OH methyl salicylate oil of wintergreen 11-17 Functional groups-6 acid chlorides have the general formula O R1 C Cl R1 is usually carbon anhydrides have the general formula O O R1 C O C R2 R1 usually is the same as R2 and neither is H O O ClC CH2CH2CH2CH2C Cl pivaloyl chlorideused to make nylon O O CH3C O C CH3 acetic anhydrideused to transfer an acetyl group 11-18 Functional groups-7 amines have one of these general formulas R1 NH2 R2 R2 R1 NH R1 N R3 R groups may be alkyl or aromatic amides have the general O formula R2 R1 C Tryptophan- an essential amino O acid CH2 CH C OH N O NH2 amine nitrogens N C CH3 amide bond N R3 All Rs may be carbon or H acetaminophen-the HO analgesic found in Tylenol (Reg) 11-19 Functional Groups-8 thiols (mercaptans) have the general formula R1 SH R1 is any carbon group disulfides have the general formula R S S R R is any carbon group Rs may be different COOH H C CH2 SH NH2 cysteine, an amino acid cystine-anfound aminoinacid important in 3-D structure of proteins. COOH COOH H C CH2 S S CH2 C H NH2 NH2 11-20 Test: Identify the groups 1-9 1 an amine 2 a carboxylic acid 3 an ester 4 an alkene 5 an aldehyde 6 an alcohol 7 a ketone 8 a thiol 9 an anhydride O 2. CH3 CH C 1. O OH CH3 C 3. NH2 4. CH2 CH CH CH2 CH3 7. C CH2 8. CH2 SH O CH3 C CH3 O H C CH HO CH CH HO CH CH2 OH O CH2 5. O 9. O O C CH3 OH 6. OH 11-21 11.2 Alkanes, CnH2n+2 The title shows the general formula for a chain alkane. The first ten alkanes are: methane CH4 hexane C6H12 ethane heptane C7H16 C2H6 propane C3H8 octane butane nonane C9H20 decane C10 H22 C4H10 pentane C5H12 C8H18 11-22 Lewis vs Condensed Formulas The Lewis dot and condensed H H C H CH4 formulas for H methane. The Lewis dot HH and condensed H C C H CH3 CH3 HH formulas for ethane . 11-23 Drawing Methane and Ethane H C H in plane H behind plane H H in front of plane H H H C H 109.5 o H Staggered form of ethane 11-24 Lewis vs Condensed Formulas-2 Lewis dot vs condensed formulas: propane. Terminal carbons condense to CH3 with the hydrogens usually to the right of the carbon. Interior carbons condense to CH2 . H H H H C C C H CH3CH2CH3 H H H 11-25 Lewis vs Condensed Formulas-3 A branch or substituent on a chain may be condensed into the chain usually after the carbon from which it branches. H HCH H H H H H C C C C C H H H Cl H H CH3CH(CH3)CHClCH2CH3 11-26 IUPAC Names The IUPAC (International Union of Pure and Applied Chemistry) is responsible for chemistry names. Before learning the IUPAC rules for naming alkanes, the names and structures of eight alkyl groups must be learned. These alkyl groups are historical names accepted by the IUPAC and integrated into modern nomenclature. 11-27 Alkyl Groups H H C H H H H C or CH3 H An alkyl group is an alkane with one hydrogen atom removed. It is named by replacing the ane of the alkane name with -yl. Methane becomes a methyl group. 11-28 Alkyl Groups-2 All six hydrogens on ethane are equivalent. Removing one H generates the ethyl group. HH HCCH HH CH3 CH2 CH2 CH3 C2H5 11-29 Alkyl Groups-3 Propane: removal of a hydrogen generates two different propyl groups depending on whether an end or center H is removed. CH3 CH2 CH3 CH3CH2CH2 n-propyl CH3CH CH3 isopropyl 11-30 Alkyl Groups-4a n-butane gives two butyl groups depending on whether an end (1o) or interior (2o) H is removed. CH3 CH2 CH2 CH3 CH3 CH2 CH2 CH2 CH3 CH CH2 CH3 n-butyl sec-butyl 11-31 Alkyl Groups-4b Isobutane gives two butyl groups 0 0 depending on whether a 1 or 3 H is removed. CH 3 CH3 CH CH3 CH3 1 C CH3 CH CH2 o isobutyl CH3 CH3 C CH3 3o C t-butyl 11-32 IUPAC Names for Alkanes-1 1. The base or parent name for an alkane is determined by the longest chain of carbon atoms in the formula. Note: the longest chain may bend and twist. It is seldom horizontal! Any carbon groups not part of the base chain are called branches or substituents. These carbon groups are also called alkyl groups. 11-33 IUPAC Names for Alkanes-1a Rules 1 applied. Find the longest chain in each molecule. (Click for answer.) A=7 B=8 CH3 A CH2CH2CH CH2CH3 B CH3 CH2 CH3CH2CH2 CH2 CH3 CH3CH2CH CH2CH CH3 11-34 IUPAC Names for Alkanes-2 2. Number the carbon atoms in the chain starting from the end with the first branch. If both branches are equally from the ends, continue until a point of difference occurs. 11-35 IUPAC Names for Alkanes-2a Number the carbon atoms correctly. Left: first branch is on carbon 3. Right: first branch is on carbon 3 (From top) not carbon 4 (If from right). 1 4 CH3 2 CH3 CH2 6 7 CH3 8 CH2CH2CH3 5 CH2CH2CH CH2CH3 CH3CH CH2CH 3 2 1 3 4 5 6 CH 2 7 CH2CH3 this branch would be on C-4 if you started at correct C-8. 11-36 IUPAC Names for Alkanes-3 3. Prefix the branches/substituents in alphabetical order before the base/stem name (longest chain). Halogens usually come first. Indicate the position of the branch on the main chain by prefixing its name with the carbon number to which it is attached. Separate numbers and letters with a hyphen. 11-37 IUPAC Names for Alkanes-3a CH 3 Name CH2 CH3 CH3 CH2 CH CH2 CH CH3 4-ethyl-2-methylhexane 11-38 IUPAC Names for Alkanes-3b Hyphenated and number prefixes are not considered when alphabetizing groups. Name the compound below. 5-sec-butyl-4-isopropylnonane CH3 CH3 CH CH2 CH3 CH CH CH CH2 CH2 CH2 CH3 CH2 CH2 CH3 CH3 11-39 IUPAC Names for Alkanes-4 When a branch/substituent occurs more than once, prefix the name with di, tri, tetra,etc. Then prefix the number to the name with a separate number for each occurance. Separate numbers with commas. eg. 3,4-dimethyl or 4,4,6-triethyl 11-40 IUPAC Names for Alkanes-4a Name CH3 CH2CH3 CH3CH CH CH2CH CH2CH3 CH3 5-ethyl-2,3-dimethylheptane ethyl>dimethyl 11-41 Test: IUPAC Names Name CH3 CH3CH CH3 CH2 CH2 CH3C CH2CH2C CH2CH3 CH3 CH2CH2CH2CH3 6-ethyl-6-isobutyl-3,3-dimethyldecane 11-42 Constitutional/Structural Isomers Constitutional/Structural Isomers differ in how atoms are connected. The two isomers of butane are shown below. The carbon atoms are connected in different patterns. CH 3 CH3 CH2 CH2 CH3 CH3 CH CH3 butane Bp –0.4 oC Mp –139 oC Isobutane Bp –12 oC Mp –145 oC 11-43 11.3 Cycloalkanes Cycloalkanes have two less hydrogens than the corresponding chain alkane. Hexane=C6H14; cyclohexane=C6H12 To name cycloalkanes, prefix cyclo to the name of the corresponding alkane. Place substituents in alphabetical order before the base name as for alkanes. For multiple substituents, use the lowest possible set of numbers. A single substituent requires no number. 11-44 Cycloalkanes-cont. H C H H C H H C H H C H H H C C H H or Cyclopropane H C H H C H H C H or Cl C H H C H H C H Cl H C CH3 H C H H C H CH3 1-chloro-3cyclohexane methylcyclohexane11-45 Cis-trans Isomers in Cycloalkanes Two groups may be on the same side (cis) of the imagined plane of the cycloring or they may be on the opposite side (trans). The two isomers are referred to geometric or cistrans isomers. E. g. Cl CH3 Cl cis-1-chloro-3-ethylcyclohexane trans-1-chloro-3-ethylcyclohexane CH3 Cl Cl Cl cis-1,4-dichlorolcyclohexane trans-1,4-dichlorocyclohexane Cl 11-46 11.4 Conformations of Alkanes Conformations differ only in rotation about carbon-carbon single bonds. Two conformations of butane are shown below. The first (staggered form) is more stable because it allows hydrogens to be farther apart and thus the atoms are less crowded. Insert Fig 11.6 11-47 Two conformations of Cyclohexane Chair form Boat form (more stable) E=equitorial A A=axial H H A H H H H E A E E A E H H E E H H A A H H 11-48 11.5 Reactions of Alkanes All alkanes undergo: Combustion to carbon dioxide and water Halogenation to haloalkanes 2 C2H6 + 7 O2 CH3CH3 + Cl2 H H + Br2 4 CO2 + 6 H2O heat or light heat or light CH3CH2Cl +HCl Br H +HBr 11-49 The End Organic Introduction Saturated Hydrocarbons 11-50