Drawing Organic Structures Functional Groups Constitutional Isomers Dr. Sheppard CHEM 2411 Spring 2015 Klein (2nd ed.) sections 2.1 – 2.6, 4.3

Draw Lewis structures… C2H6 CH4O C3H6 (contains C=C) C4H10 (multiple possible answers)

More Lewis structures… CH5N CHN HNO3 Remember… Keep in mind total available valence electrons Try to minimize formal charges Patterns for formal charge

Molecular Representations Example: isopropyl alcohol (C3H80) Lewis structure Show all bonds, atoms, lone pairs Partially condensed/Condensed structure Omit some bonds (C─C, C─H, O─H, N─H) Often omit lone pairs Not the same as a molecular formula Skeletal structure/Bond-line structure/Line-angle drawing Show bond framework as lines C atoms at intersections of lines (bonds) and end of each line H atoms bonded to C are not shown Heteroatoms (atoms other than C and H) are shown

Drawing line-angle structures Name Lewis structure Condensed structure Line-angle drawing Acetone Butane 1-Butene Cyclohexane Benzene

Lone Pairs on Line-angle Drawings Formal charges must be shown Lone pairs may be omitted, and can be determined from structure

Lone Pairs on Line-angle Drawings

Interpreting Line-angle Structures What is the molecular formula for the following: What is the molecular formula for adrenaline? What is the molecular formula for thalidomide?

Molecular Representations Which Lewis structure is correct?

Molecular Representations Draw partially condensed and line-angle structures for this condensed structure: (CH3)3CCH2COCHCH2 How many hydrogens on each carbon atom?

3D Organic Structures Remember, carbons are tetrahedral Use dashes and wedges to show 3D structure

Functional Groups Collection of atoms at a site within a molecule with a common bonding pattern Reacts in a typical way, generally independent of the rest of the molecule Four broad classes Hydrocarbons Compounds containing O Compounds containing N Compounds containing S or P

1. Hydrocarbons Alkane: single bonds, sp3 carbons Cycloalkane: carbons form a ring Alkene: double bond, sp2 carbons Cycloalkene: double bond in ring Alkyne: triple bond, sp carbons Aromatic (arene): contains a benzene ring Not a hydrocarbon, but related… Alkyl halide: R─X R = any carbon group X = halogen

2. Compounds containing oxygen Alcohol: R─OH Ether: R─O─R' Carbonyl group: C=O Aldehyde: RCHO Ketone: RCOR'

Carboxylic acids and their derivatives Carboxylic Acid: RCOOH Acid Chloride: RCOCl Ester: RCOOR' (RCO2R’) Amide: RCONH2 Acid Anhydride: RCO2COR

3. Compounds containing nitrogen Amines: RNH2, RNHR', or R3N Amides: RCONH2, RCONHR, RCONR2 Nitrile: RCN

4. Compounds containing S or P Phosphates (PO42-) Thiol (R─SH) Sulfides (R─S─R) Sulfoxides (S=O) Thioester (RCOSR)

Functional Groups Identify the functional group(s) present in the following molecules.

Functional Groups Identify the functional groups present in thalidomide: Draw as many structures as you can with the molecular formula C4H8O2. Identify the functional groups present in each structure.

Isomers Isomers have the same molecular formula, but different arrangements of atoms Constitutional isomers differ in their connectivity Stereoisomers differ in the spatial arrangement/orientation of their atoms

Constitutional Isomers Molecules with the same molecular formula, but different connectivity Same number and kinds of atoms Differ in which atoms are bonded Example: C4H10 Straight-chain (“normal”) alkane vs. branched-chain alkane

Constitutional Isomers

Constitutional Isomers Are the following pairs of molecules constitutional isomers, the same molecule, or neither? (a) (b) (c) (d)