Lecture Presentation. Chapter 20. Organic Chemistry. Sherril Soman Grand Valley State University Pearson Education, Inc.

Transcription

1 Lecture Presentation Chapter 20 Organic Chemistry Sherril Soman Grand Valley State University

2 Fragrances and Odors Our sense of smell helps us identify food, people, and other organisms, and alerts us to dangers such as polluted air or spoiled food. Odorants must be volatile. However, many volatile substances have no scent at all. Most common smells are caused by organic molecules. The study of compounds containing carbon combined with one or more of the elements hydrogen, nitrogen, oxygen, and sulfur, including their properties and their reactions, is known as organic chemistry.

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4 What Is Organic Chemistry? Organic chemistry is a branch of chemistry that focuses on compounds that contain carbon. Except CO, CO 2, carbonates, and carbides Even though organic compounds only contain a few elements, the unique ways carbon atoms can attach together to form molecules leads to millions of different organic compounds.

5 The Chemistry of Life Life as we know it is because of organic chemistry. Organic molecules can be very large and complex. It is this complexity of large organic molecules that allows the complex functions of the cells to occur.

6 Differences Between Organic and Inorganic Compounds Organic compounds are easily decomposed into simpler substances by heating, but inorganic substances are not. Inorganic compounds were readily synthesized in the lab, but synthesis of organic compounds in the lab is hard.

7 What s Special About Organic Compounds? Organic compounds tend to be molecular. They are mainly composed of just six nonmetallic elements. C, H, O, N, S, and P Compounds are found in all three states. Solids, liquids, and gases Solids tend to have low melting points Solubility in water varies depending on which of the other elements are attached to C and how many there are. CH 3 OH is miscible with water; C 10 H 21 OH is insoluble.

8 What s So Special About Carbon? Carbon atoms can do some unique things that other atoms cannot. Carbon can bond to as many as four other atoms. Bonds to carbon are very strong and nonreactive.

9 What s So Special About Carbon? Carbon atoms can attach together in long chains. Carbon atoms can attach together to form rings. Carbon atoms can form single, double, or triple bonds.

10 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

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13 Formulas Molecular formulas show the kinds of atoms in the molecule, but they do not show 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.

14 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 one identical group attached to same previous central atom Unless () group is listed first, in which case attached to next central atom

15 Uses of Hydrocarbons

16 Uses of Hydrocarbons

17 Uses of Hydrocarbons

18 Physical Properties of Aliphatic Hydrocarbons Boiling points and melting points increase as the size of the molecule increases. Nonpolar molecules Main attractive forces are dispersion forces Less dense than water Insoluble in water

19 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 C n H 2n+2. Ring alkanes have all C C single bonds, but have fewer hydrogens than a chain with the same number of carbons.

20 Unsaturated Hydrocarbons Unsaturated hydrocarbons have one or more C C double bonds or C C triple bonds. Unsaturated aliphatic hydrocarbons that contain C C are called alkenes. The general formula of a monounsaturated chain alkene is C n H 2n. Remove two more H for each additional double bond. Unsaturated aliphatic hydrocarbons that contain C C are called alkynes. The general formula of an alkyne with one triple bond is C n H 2n 2. Remove four more H for each additional triple bond.

21 Aromatic Hydrocarbons Aromatic hydrocarbons contain a ring structure that seems to have C C, but doesn t behave that way. The most prevalent example is benzene. C 6 H 6 Other compounds have the benzene ring with other groups substituted for some of the hydrogens.

22 Carbon Skeleton 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

23 Formulas

24 Isomerism Isomers are different molecules with the same molecular formula. Structural isomers are isomers that have a different pattern of atom attachment. Also known as constitutional isomers Stereoisomers are isomers with the same pattern of atom attachments, but the atoms have a different spatial orientation.

25 Structural Isomers of C 4 H 10 Butane, BP = 0 C Isobutane, BP = 12 C

26 Rotation about a Bond Is Not Isomerism

27 Alkanes Also know as paraffins Aliphatic General formula C n H 2n+2 for chains Very unreactive Come in chains or/and rings CH 3 groups at ends of chains, CH 2 groups in the middle Saturated Branched or unbranched

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30 Physical Properties of n Alkanes

31 Naming Each name consists of three 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 o -ane, -ene, -yne Certain functional groups

32 Naming Alkanes 1. Find the longest continuous carbon chain. 2. Number the chain from end closest to a branch. If first branches are equal distance, use next substituent 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

33 Prefixes

34 Alkyl Groups

35 Alkenes Also known as olefins Aliphatic, unsaturated C C double bonds Formula for one double bond = C n H 2n. Subtract 2 H from alkane for each double bond. Trigonal shape around C Flat Polyunsaturated = many double bonds

36 Alkenes ethene = ethylene H H C C H H propene = propylene H H C C H C H 3 Produced by ripening fruit Used to make polyethylene Used to make polypropylene

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38 Alkynes Also known as acetylenes Aliphatic, unsaturated C C triple bond Formula for one triple bond = C n H 2n 2. Subtract 4 H from alkane for each triple bond. Linear shape Internal alkynes have both triple bond carbons attached to C. Terminal alkynes have one carbon attached to H.

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40 Alkynes Ethyne = acetylene Used in welding torches

41 Physical Properties of Alkynes Higher boiling points than similar sized alkenes Similar size = same number of carbons More pi bond = more polarization = higher boiling point Slightly higher densities than similar alkenes There are no alkyne cis or trans isomers. Internal alkynes have higher boiling points than terminal alkynes. With the same number of C

42 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.

43 Reactions of Hydrocarbons All hydrocarbons undergo combustion. Combustion is always exothermic. About 90% of U.S. energy generated by combustion CH 3 CH 2 CH 3 (g) + 5 O 2 (g) 3 CO 2 (g) + 4 H 2 O(g) CH 2 CHCH 2 CH 3 (g) + 6 O 2 (g) 4 CO 2 (g) + 4 H 2 O(g) CH CCH 3 (g) + 4 O 2 (g) 3 CO 2 (g) + 2 H 2 O(g)

44 Chemical Energy Burning hydrocarbons releases heat and light energy. Combustion Alkane + oxygen carbon dioxide + water Larger alkane, more heat released

45 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 Methane + chlorine à chloromethane + HCl

46 Alkene and Alkyne Reactions: Addition Adding a molecule across the multiple bond Hydrogenation = adding H 2 Converts unsaturated molecule to saturated Alkene or alkyne + H 2 alkane Generally requires a catalyst Halogenation = adding X 2 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.

47 Addition Reactions

48 Aromatic Hydrocarbons Contain benzene ring structure Even though they are often drawn with C C, they do not behave like alkenes.

49 Resonance Hybrid The true structure of benzene is a resonance hybrid of two structures.

50 Naming Monosubstituted Benzene Derivatives (Name of substituent)benzene Halogen substituent = change ending to o Or name of a common derivative

51 Naming Benzene as a Substituent When the benzene ring is not the base name, it is called a phenyl group.

52 Naming Disubstituted: Benzene Derivatives Number the ring starting at attachment for first substituent, and then move toward the second. Order substituents alphabetically. Use di- if both substituents are the same.

53 Naming Disubstituted: Benzene Derivatives Alternatively, use relative position prefix. Ortho- = 1,2; meta- = 1,3; para- = 1,4 2-chlorotoluene ortho-chlorotoluene o-chlorotoluene 3-chlorotoluene meta-chlorotoluene m-chlorotoluene 4-chlorotoluene para-chlorotoluene p-chlorotoluene

54 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 shows 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. Because the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol.

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56 Alcohols R OH Ethanol = CH 3 CH 2 OH Grain alcohol = fermentation of sugars in grains Alcoholic beverages Proof number = 2 times percentage of alcohol Gasohol Isopropyl alcohol = (CH 3 ) 2 CHOH 2-propanol Rubbing alcohol Poisonous Methanol = CH 3 OH Wood alcohol = thermolysis of wood Paint solvent Poisonous

57 Naming Alcohols Main chain contains 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 higher precedence group present.

58 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 = H 2 C=O Pungent gas Formalin = a preservative Wood smoke, carcinogenic Acetone = CH 3 C(=O)CH 3 Nail-polish remover

59 Naming Aldehydes and Ketones Main chain contains C O. Unless COOH present Number main chain from end closest to C O. For aldehydes, give base name -al ending. Always on C1 For ketones, give base name -one ending and place number of C on chain where C O attached in front.

60 Carboxylic Acids RCOOH Sour tasting Weak acids Citric acid ü Found in citrus fruit Ethanoic acid = acetic acid ü Vinegar Methanoic acid = formic acid ü Insect bites and stings

61 Naming Carboxylic Acids Carboxylic acid group always on end of main chain Has highest naming precedence of functional groups C of group always C1 Position not indicated in name Change ending to -oic acid

62 Examples of Naming Carboxylic Acids

63 Esters R COO R Sweet odor Made by reacting carboxylic acid with an alcohol R a COOH + R b OH R a COOR b + H 2 O

64 Naming Esters Carboxylic acid group always on end of main chain Unless carboxylic acid group present C of ester group on C1 Position not indicated in name Begin name with alkyl group attached to O. Name main chain with -oate ending.

65 Condensation Reactions A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water. Esters are made by the condensation reaction between a carboxylic acid and an alcohol. ü The reaction is acid catalyzed.

66 Condensation Reactions A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water.

67 Condensation Reactions A condensation reaction is any organic reaction driven by the removal of a small molecule, such as water. Acid anhydrides are made by the condensation reaction between to carboxylic acid molecules. ü The reaction is driven by heat.

68 Synthesis of Aspirin (Acetylsalicylic Acid)

69 Ethers Ethers have the general formula ROR. The two R groups may be different or identical.

70 Ethers Diethyl ether is the most common ether. It is useful as a laboratory solvent and can dissolve many organic compounds. It has a low boiling point.

71 Amines N containing organic molecules Very bad smelling Form when proteins decompose Organic bases Name alkyl groups attached to the N, then add -amine to the end.

72 Amines Many amines are biologically active. Dopamine a neurotransmitter Epinephrine an adrenal hormone Pyridoxine vitamin B 6 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

73 Polymers Polymers are very large molecules made by repeated linking together of small molecules. Monomers

74 Polymers Natural polymers are polymers found in both the living and nonliving environment. Modified natural polymers are natural polymers that have been chemically altered. Synthetic polymers are polymers made in a lab from one, two, or three small molecules linked in a repeating pattern. Plastics, elastomers (rubber), fabrics, adhesives Composites are materials made of polymers mixed with various additives. Additives such as graphite, glass, metallic flakes

75 Natural Polymers Polysaccharides polymers made of repeating small sugar molecule units Cellulose (cotton) Starch Proteins polymers made of repeating amino acid units Nucleic acids (DNA) polymers made of repeating nucleotide units Natural latex rubber polyisoprene Shellac a resin secreted by lac bugs Gutta-percha a polyisoprene latex from the sap of the gutta-percha plant Used to fill space for root canal Amber, lignin, pine rosin resins from trees Asphalt polymeric petroleum

76 Modified Natural Polymers Cellulose acetate an ester of cellulose and acetic acid Rayon Film Vulcanized rubber latex rubber hardened by cross-linking with sulfur Nitrocellulose an ester of cellulose with nitric acid Gun cotton Celluloid Ping-Pong balls Casein a polymer of the protein casein made by treating cow s milk with acid Buttons, moldings, adhesives

77 Polymerization Polymerization is the process of linking the monomer units together. There are two processes by which polymerization may proceed addition polymerization and condensation polymerization. Monomer units may link head to tail, or head to head, or tail to tail during polymerization. Head to tail most common Regular pattern gives stronger attractions between chains than random arrangements

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79 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 the addition of an initiator The process is a chain reaction. Each added unit ready to add another

80 Condensation Polymerization Monomer units are joined by removing small molecules from the combining units. Polyesters, polyamides lose water No initiator is needed. The process is a chain reaction. Each monomer has two reactive ends, so the chain can grow in two directions.

81 Characteristics of Plastics Transparent or translucent Chemical resistance Thermal and electrical insulators Low density Varying strengths Kevlar Mold or extrude Elasticity Regain original shape if quick stress applied Foamed Tend to soften when heated, rather than quickly melt

82 Lecture Presentation Chapter 21 Biochemistry Sherril Soman Grand Valley State University

83 Biochemistry Biochemistry is the study of the chemistry of living organisms. Much of biochemistry deals with the large, complex molecules necessary for life as we know it. However, most of these complex molecules are actually made of smaller, simpler units; they are biopolymers. There are four main classes of biopolymers lipids, proteins, carbohydrates, and nucleic acids.

84 Lipids Chemicals of the cell that are insoluble in water, but soluble in nonpolar solvents. Fatty acids, fats, oils, phospholipids, glycolipids, some vitamins, steroids, and waxes Structural components of cell membrane Because they don t dissolve in water Long-term energy storage Insulation

85 Fatty Acids Carboxylic acid (head) with a very long hydrocarbon side chain (tail). Saturated fatty acids contain no C C double bonds in the hydrocarbon side chain. Unsaturated fatty acids have C C double bonds. Monounsaturated have 1 C C. Polyunsaturated have more than 1 C C.

86 Fatty Acids Myristic acid Oleic acid C 18 H 34 O 2 a monounsaturated fatty acid

87 Structure and Melting Point Larger fatty acid = higher melting point Double bonds decrease melting point More DB = lower MP Saturated = no DB Monounsaturated = 1 DB Polyunsaturated = many DB

88 Effect on Melting Point Because fatty acids are largely nonpolar, the main attractive forces are dispersion forces. Larger size = more electrons = larger dipole = stronger attractions = higher melting point More straight = more surface contact = stronger attractions = higher melting point

89 Triglycerides Triglycerides differ in the length of the fatty acid side chains and degree of unsaturation. Side chains range from 12 to 20 C. Most natural triglycerides have different fatty acid chains in the triglyceride, simple triglycerides have three identical chains. Saturated fat = all saturated fatty acid chains Warm-blooded animal fat Solids Unsaturated fats = some unsaturated fatty acid chains Cold-blooded animal fat or vegetable oils Liquids

90 Phospholipids Phospholipids are esters of glycerol in which one of the OH groups of glycerol esterifies with phosphate. Other two OH are esterified with fatty acids Phospholipids have a hydrophilic head due to phosphate group, and a hydrophobic tail from the fatty acid hydrocarbon chain. Part of lipid bilayer found in animal cell membranes

91 Lipid Bilayer

92 Steroids Characterized by four linked carbon rings Mostly hydrocarbon-like Dissolve in animal fat Mostly have hormonal effects Serum cholesterol levels linked to heart disease and stroke Levels depend on diet, exercise, emotional stress, genetics, etc. Cholesterol synthesized in the liver from saturated fats.

93 Carbohydrates Carbon, hydrogen, and oxygen Ratio of H:O = 2:1 Same as in water Polyhydroxycarbonyls have many OH and one C O. Aldose when C O is aldehyde Ketose when C O is ketone The many polar groups make simple carbohydrates soluble in water. Blood transport Also known as sugars, starches, cellulose, dextrins, and gums

94 Classification of Carbohydrates Monosaccharides cannot be broken down into simpler carbohydrates. Triose, tetrose, pentose, hexose Disaccharides are two monosaccharides attached by a glycosidic link. Lose H from one and OH from other Polysaccharides are three or more monosaccharides linked into complex chains. Starch and cellulose are polysaccharides of glucose.

95 Polysaccharides Also known as complex carbohydrates Polymer of monosaccharide units bonded together in a chain The glycosidic link between units may be either α or β. In α, the rings are all oriented the same direction. In β, the rings alternate orientation.

96 Proteins Involved in practically all facets of cell function Polymers of amino acids

97 Amino Acids NH 2 group on carbon adjacent to COOH - α-amino acids About 20 amino acids found in proteins 10 synthesized by humans, 10 essential Each amino acid has a three-letter abbreviation. Glycine = Gly High melting points Generally decompose at temp > 200 C Good solubility in water Less acidic than most carboxylic acids and less basic than most amines

98 Basic Structure of Amino Acids

99 Basic Structure of Amino Acids

100 Amino Acids Building blocks of proteins Main difference between amino acids is the side chain R group Some R groups are polar, while others are nonpolar. Some polar R groups are acidic, while others are basic. Some R groups contain O, others contain N, and others contain S. Some R groups are rings, while others are chains.

101 Nucleic Acids Carry genetic information DNA molar mass = 6 to 16 million amu RNA molar mass = 20 K to 40 K amu Made of nucleotides Phosphoric acid unit 5-carbon sugar Cyclic amine (base) Nucleotides are joined by phosphate linkages.

102 DNA Deoxyribonucleic acid Sugar is deoxyribose. DNA is made up of the following amine bases: Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Two DNA strands wound together in double helix Each of the 10 trillion cells in the body has the entire DNA structure.

103 RNA Ribonucleic acid Sugar is ribose. RNA is made of up of the following amine bases: Adenine (A) Guanine (G) Cytosine (C) Uracil (U) Single strands wound in helix

104 DNA Structure DNA made of two strands linked together by H-bonds between bases Strands are antiparallel One runs 3' 5', while other runs 5' 3'. Bases are complementary and directed to the interior of the helix. A pairs with T, and C with G.

105 Base Pairing Base pairing generates the helical structure. In DNA, the complementary bases hold strands together by H-bonding. Allow replication of strand

106 DNA Replication When the DNA is to be replicated, the region to be replicated uncoils. This H-bond between the base pairs is broken, separating the two strands. With the aid of enzymes, new strands of DNA are constructed by linking the complementary nucleotides and the original strand together.

107 DNA Replication

108 Protein Synthesis Transcription translation In the nucleus, the DNA strand at the gene separates and a complementary copy of the gene is made in RNA. Messenger RNA = mrna The mrna travels into the cytoplasm where it links with a ribosome. At the ribosome, each codon on the RNA codes for a single amino acid, and these are joined together to form the polypeptide chain.