CHEMISTRY 104 – Help Sheet #2 Chapter 24 (Part I) Prepared by Dr. Tony Jacob http://www.chem.wisc.edu/areas/clc (Resource page) Nuggets: Drawing/Naming Organic Molecules, Functional Groups (Part I) NAMING MOLECULES: 1. Find longest C chain 2. Number the longest C chain to give smallest numbers for functional group or side branches 3. Prefixes (#carbon atoms): Meth (1), Eth (2), Prop (3), But (4), Pent (5), Hex (6), Hept (7), Oct (8), Non (9), Dec (10) 4. Suffixes: “ane” for alkanes, “ene” for alkenes, etc.; see below for other suffixes 5. a. Branches: add "yl" to prefix; e.g., 1-C branch = meth+yl = methyl; 2-C branch = eth+yl = ethyl; etc. b. Duplicate branches: di (2), tri (3), tetra (4) as in two 2-C branches = diethyl c. Alphabetize multiple branches; do not alphabetize on the di, tri, or tetra ethyl before propyl; ethyl before dimethyl (alphabetize on the “e” and “m,” ignore the “di”) d. Every branch must have a number (carbon position) associated with it; every number has a branch e. Commas between numbers; dashes (“-”) between numbers and letters 6. Alkene functional group: check for cis/trans isomers Example: Name the molecule shown. 1. Find longest C chain (dashed rectangular box) – 7 carbons long; prefix = hept 2. All C–C single bonds; suffix = ane 3. Find branches off chain (dashed ovals). One branch = 1C long = methyl; two branches = 2C long = each is ethyl – since two identical branches use diethyl 4. Number chain both ways; choose numbering scheme to yield smaller numbers for branches (bottom bold numbers). Functional groups (e.g., an alcohol, get higher priority in numbering chain); this molecule has no functional group 5. Alphabetize branches (diethyl before methyl; alphabetize on “e” and “m”). 6. Each branch gets a number: 2-methyl; 3,4-diethyl 7. commas (,) between numbers; dashes ( - ) between numbers and letters Name: 3,4-diethyl-2-methylheptane 12345123456767 FUNCTIONAL GROUPS (the first 7): C and H compounds (hydrocarbons) and –O– structures Functional Group Suffix Formula Other Info Alkane ane C–C saturated; tetrahedral; sp3; 109.5˚; CnH2n+2; free rotation around C-C σ-bond; Alkene ene C=C unsaturated; trigonal planar; sp2; 120˚; CnH2n; geometric isomers (cis/trans); can’t rotate thru C=C → π bond; σ + π Alkyne yne C≡C unsaturated; linear; sp; 180˚; CnH2n-2; σ + 2π Cyclic cyclo + (ane, ene, or yne) Ex: or cycloalkane-unsaturated; strained tetrahedral; sp3; CnH2n; not planar Aromatic benzene, C6H6 = planar molecule; trigonal planar geometry at each C; BOC–C = 1.5; sp2; 120˚; resonance Alcohol (an)ol R-O-H (R ≠ H); 1˚ (primary), 2˚ (secondary), 3˚ (tertiary); H-bonding; polar; e.g., 3-methyl-2-butanol Ether “ether" R-O-R' R, R’ ≠ H; polar; alphabetize branches+”ether” e.g., methylpropylether: Omethylpropyl OH1234Alkanes: only carbon–carbon single bonds; a sigma (σ) bond between C atoms; saturated molecules; formula CnH2n+2; often denoted as “R”; C–C bond can rotate Alkenes: at least one carbon–carbon double bond = σ + π bonds; formula CnH2n (one double bond); R=R'; C=C double bond can’t rotate because of π bond; has cis and trans geometric isomers: unsaturated molecule Alkynes: at least one carbon–carbon triple bond = σ + 2π bonds; formula CnH2n-2 (one triple bond); R≡R'; C≡C triple bond can’t rotate because of π bonds; unsaturated molecule Cyclic: ring compounds; formula CnH2n (1 ring); 3-membered ring unstable; 4-membered ring somewhat stable; 5-membered ring stable and almost planar; 6-membered ring stable puckered (boat or chair configuration) Aromatic: for Chem 104 the focus is on benzene, C6H6, or a derivative; C–C bonds equivalent; BOC–C = 1.5; planar molecule; naming: "omp": ortho = 1,2-disubstituted, meta = 1,3-disubstituted, para = 1,4-disubstituted Alcohol: a –OH (hydroxyl) group attached; (R—OH); H-bonding primary (1˚): C with –OH has 1 C atom attached; secondary (2˚): C with –OH has 2 C atoms attached tertiary (3˚): C with –OH has 3 C atoms attached to it Ether: bridging oxygen atom; (R—O—R'); R and R' ≠ H otherwise it becomes an alcohol Hydrocarbons – only hydrogen and carbon: colorless, nonpolar Properties C1 – C4 → gases; C5 – C17 → liquids; C18 – higher → solids Nonpolar; immiscible (doesn’t mix) in water; found as a wide range of chain lengths (fossil fuels); longer chained fossil fuels made smaller by cracking; branches added to molecules by reforming – more branches allows for better combustion; octane rating refers to a comparison to isooctane, 2,2,4-trimethylpentane DRAWING MOLECULES: H, F, Cl, Br, I – 1 bond; O – usually 2 bonds; N – usually 3 bonds; C – 4 bonds Lewis – all bonds and e- drawn Expanded – all bonds drawn Dash/Wedge Condensed Structure Line Notation Variations: Condensed Structures with some bonds drawn CHHHC CHClHHH C C CHHH HClHHH CCCH HH H HClHH CH3CHClCH3 Cl CH3CHCH3Cl CH3CH CH3Cl 1. Draw the following molecules in the Lewis dot format showing all bonds, atoms, and e-, and in line format. a. CH3CH2CH2CH2CH2CH3 b. (CH3)2CC(CH3)2 c. CHCCH3 2. Give the IUPAC name for each of the following molecules. a. H CHHCHHCHHCHHCHHCHHH b. CH3CH2CH2CH CH3CH3 c. CH3CHCH2CH CH2CH3CH3CH CH3CH3 d. CH3CHCH3C CH2CH3CH2CH3CH3 e. CH3C CH3CH3CH3 f. CH CH2CH2CH2CH2CH3CH3CH2CH2CH3 g. C C CH3CH3CH3CH3CH3CH3 h. CH3CH2CH CH2CH3CH2CH33. Using line notation, draw the organic molecules given their names. a. 2,2,4-trimethylpentane b. 1,1,2-trichlorohexane c. 3,4,5-triethyl-2, 6-dimethyloctane d. 1,1,2-trichlorocyclopentane e. 3-ethyl-4-methyl-2-pentanol f. 1-ethyl-2,4-dimethylbenzene g. ortho-dichlorobenzene h. 4-methyl-2-hexyne i. 2,3,3-tribromo-1-butene j. methylethylether k. dipropylether 4. Give the IUPAC name for each of the following molecules. a. b. c. d. e. f. g. h. i. j. k. l. OH m. OH n. O 5. Which functional group could the molecule, C35H70, contain? a. alkane b. alkene c. alkyne d. alcohol e. more info needed 6. Draw the two resonance structures using line notation that are used to represent benzene, C6H6. 7. Which functional group is polar? a. cycloalkane b. alkene c. aromatic d. ether e. none are polar 8. Which functional group will have sp hybridization? a. cycloalkane b. alkene c. aromatic d. ether e. none willANSWERS 1. a. H