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CHM 103 GENERAL CHEMISTRY SPRING QUARTER 2004 Lesson Plan – 6/8/2004 A. Quiz at 12:00. B. Hand in your extra credit (pH meter calibration) assignments. C. Organic Chemistry (Just a Wee Taste) 1. Introduction 2. Saturated Hydrocarbons 3. Unsaturated Hydrocarbons 4. Aromatic Hydrocarbons 5. Organics Containing Oxygen 6. Organics Containing Nitrogen 7. Isomerism 8. Polymers D. Introduction 1. >90% of all chemical compounds contain carbon. Reason: It is easy to form chains and rings containing C-C bonds. 2. Organics tend to be molecular (rather than ionic). 3. Four covalent bonds on a carbon atom. 4. Favorite bonding partners: C, H, O, N, F, Cl, Br, I, S, P. 5. Numbers of bonds: C 4 H, F, Cl, Br, I 1 O, S 2 N, P 3 E. Saturated Hydrocarbons (Alkanes) 1. Made up only of C and H. 2. C’s are formed into chains (except methane). 3. C--C bonds are all single bonds with (nearly) free rotation. 06/27/2017 01:04 Page 1 of 8 D:\478161095.doc 4. Tetrahedral geometry about C – in methane (CH4), all H--H distances are the same. 5. Chains may be “straight” or branched. Butane and 2-methylpropane (also called n-butane and isobutane) are structural isomers. 6. Structural isomers are distinct chemical compounds with different boiling points, etc., despite having the same atomic compositions and molecular weights. 06/27/2017 01:04 Page 2 of 8 D:\478161095.doc 7. Typical alkanes: a. Natural gas: methane (CH4) and ethane (C2H6). b. Bottle gas: propane (C3H8) and butane (C4H10). c. Gasoline: mixture in C5 to C9 range. d. Fuel oil. e. Lubricating oil. f. Asphalt. g. Crude oil (a mixture with wide range of b. p.’s). Separated into useful components by fractional distillation. F. Unsaturated Hydrocarbons (Alkenes and Alkynes) 1. Characterized by one or more multiple bonds (we will consider only simple alkenes, having one double bond, and simple alkynes, having one triple bond). 2. Alkenes a. One carbon-carbon double bond. b. General formula: CnH2n c. No rotation about the double bond. d. The double bond is considerably more reactive than a C--C single bond. e. Geometry at double bond (>C=C<) is planar. f. Ethylene (ethane) and propylene (propene) are simplest examples. 06/27/2017 01:04 Page 3 of 8 D:\478161095.doc 3. Alkynes a. b. c. d. One carbon-carbon triple bond. General formula: CnH2n-2 Geometry at triple bond is linear. Acetylene is simplest example. G. Aromatic Hydrocarbons and Their Derivatives 1. Characterized by planar, ringed structures. 2. Benzene, C6H6, is simplest example. 3. Benzene has a six membered ring structure 6 identical C—C bonds the bond angles are all 120° the 6 carbons are coplanar valence bond picture (resonance hybrid structure): molecular orbital picture: each vertex represents a C atom one H is bonded to each C (H atoms and C—H bonds not shown) 06/27/2017 01:04 Page 4 of 8 D:\478161095.doc the circle represents the 6 delocalized “pi” electrons 4. Some Common Derivatives of Benzene 5. Condensed Ring Structures condensed rings are generally planar graphite and coal contain large sheets of condensed rings H. Organics Containing Oxygen 1. Alcohols: Organics containing –O—H (hydroxyl) groups a. Methanol (methyl alcohol): CH3OH Imagine methane (CH4) with one H replaced by OH (but it is not made this way) Generally manufactured from synthesis gas (CO + H2) under conditions of high temperature and pressure and using catalyst: CO(g) + 2H2(g) CH3OH(g) b. Ethanol (ethyl alcohol): C2H5OH Generally made by fermentation of sugar Industrial grade made by reacting ethylene with water (and sulfuric acid as catalyst) c. Multi-Hydroxyl Alcohols 06/27/2017 01:04 Page 5 of 8 D:\478161095.doc 2. Carboxylic Acids: Organics containing –COOH (carboxyl) groups a. Carboxyl structure b. Formic Acid (HCOOH): the simplest carboxylic acid c. Acetic Acid (CH3COOH): the most familiar This is the same acetic acid we classed as a weak acid in chapter 13 and wrote: HC2H3O2. Even if we write it as CH3COOH, we can still react it with strong base to produce an acetate salt: A similar reaction can convert stearic acid into a soap. 3. Esters: Organics containing –COO– groups (ester linkages) a. Structure of an ester linkage: b. Make an ester by reacting an alcohol with a carboxylic acid to eliminate water and generate an ester: c. Names of esters: The first name of the ester is the same as the first name of the alcohol. The second name of the ester is like the first name of the acid, except that you change the “-ic” suffix to “-ate.” 06/27/2017 01:04 Page 6 of 8 D:\478161095.doc Example: the ester obtained from the reaction of ethyl alcohol and formic acid is called “ethyl formate.” 4. Other Oxygen-containing Organics – See Table 22.1 a. Ethers (–O–) b. Aldehydes (–CHO) c. Ketones (–CO–) I. Organics Containing Nitrogen 1. (Primary) Amines: Organics containing –NH2 (primary amine) groups a. Simplest member is methyl amine: CH3NH2 b. Another is aniline: C6H5NH2 (we saw this earlier as a benzene derivative) 2. Amides: Organics containing carbonyl linked to nitrogen a. Structures of amides b. Amide types (a), (b), and (c) all contain an amide linkage [–(C=O)NH–] c. React an amine with a carboxylic acid to eliminate water and generate an amide Amide type (a) is the reaction product of ammonia with a carboxylic acid, for example: CH3COOH + NH3 CH3CONH2 + H2O Amide type (b) is the reaction product of a primary amine, such as methyl amine, with a carboxylic acid, for example: CH3COOH + CH3NH2 CH3CONHCH3 + H2O Amide type (c) is the reaction product of a secondary amine, such as dimethyl amine, with a carboxylic acid. 3. Amino Acids: Organics containing both a carboxyl group and an amine group 06/27/2017 01:04 Page 7 of 8 D:\478161095.doc a. If the amine is substituted on the carbon that is next to the carboxyl group, we have an alpha-amino acid. Some examples, recovered from proteins, are shown in the following table: b. An amino acid is capable of forming two amide linkages, one with its N, the other with the C in its carboxyl group. c. Groups of alpha-amino acids can react to form chains whose backbones contain repeated peptide units: –NHCHRCO– , for example: (The R groups are characteristic of the various amino acids.) 06/27/2017 01:04 Page 8 of 8 D:\478161095.doc