Essentials of Organic Chemistry Chemistry 304 Thomas J. Wiese, Ph.D. Associate Professor of Chemistry Fort Hays State University

Introduction Roll Call Syllabus Tests and Grading Approximate grading scale:

Course Overview Ch. 1-9, 18? The way to study: scan assigned reading material before class listen during class and take notes read assigned material (SQ3R) and supplement class notes review the weeks notes every weekend begin good study habits early! pay attention to details I point out

Introduction to Organic Chemistry (Review of Freshman Chemistry)

Element Element- pure substance composed of only one type of atom H vs. He vs. Unh

Atom Atom- the smallest particle of matter Composed of protons, neutrons and electrons

Compound vs. molecule Compound- atoms of two or more elements bonded together Molecule has two meanings Atoms of the same element bonded together A single compound moiety

Atomic Structure A nucleus containing protons and neutrons, surrounded by a cloud of electrons s-electrons p-electrons (px, py, and pz) (d-electrons and f-electrons)

Electron Configurations Two electrons (e – ) per orbital Principle energy levels and the Aufbau principle 1 contains only s e – 2 contains s and p e – 3 contains s, p and d e – 4 contains s, p, d and f e – Spin-pair rule Hunds rule

6/9/04

Bonds Ionic bond- electrostatic interaction when metal and nonmetal interact (NaCl as an example) Covalent bond-A chemical bond that involves sharing of electron pairs (not all same) Two shared electrons = 1 bond (H 2 )

Molecular Properties Ionic compounds solid high mp/bp conductors vs. Covalent compounds solid or liquid or gas low mp/bp insulators

Other Bond Issues Polar covalent bond (O—H) Double bond (O 2 ) and triple bond (N 2 ) Coordinate covalent bond (NH 4 + formation)

Charge and Formal Charge There is a formal charge for each atom of a compound

Review Questions Are the following bonds polar or nonpolar? C-C C-H C-O C-N What are the formal charges for the carbonate ion, CO 3 2- ?

Intermolecular Forces London forces (AKA van der Waals) Dipole-dipole interactions Hydrogen bond

6 Forces between Molecules I. London Forces all particles have London forces larger particles have larger London forces only force between noble gases and nonpolar compounds about 1/1000 as strong as a covalent bond

7 Forces between Molecules II. Dipole-Dipole Interactions different from London forces only in permanence somewhat stronger than London forces because permanent occurs in all polar molecules weaker than ionic bond because only  + or  

8 Forces between Molecules III. Hydrogen Bonds rare occur between one H which is covalently bonded to an N, O, or F atom and a second N, O, or F atom strongest of three intermolecular forces

6/10/04

Solubility “Like dissolves like” Solvent- Solute- 4 C

Shapes of Molecules Linear Bent Pyramidal Tetrahedral Triangular others

Organic Chemistry Organic chemistry- the chemistry of carbon- containing compounds

Forms of Elemental Carbon Graphite Diamond Buckminsterfullerene - Nobel prize 1996 “Amorphous”

Carbon Atomic structure –6 p –Predominately 6 neutrons –6 e – group IVA –4 valence electrons –oxidation state “±4” –form 4 bonds in reactions –tetrahedral

6/14/04

Atomic Orbitals electron configuration of C 1s 2,2s 2,2p 2 We might expect C to form two bonds ( the 2 unpaired p electrons)  We know that C forms 4 bonds  We might expect that CH 4 would have 1 s-s bonds and 3 s-p bonds.  We know that all C–H bonds are equivalent 

Hybrid Atomic Orbitals Hybrid atomic orbitals is a theory used to reconcile the discrepancy between what atomic orbital theory predicts, and what is seen experimentally. Fig 1.12: C has 4 sp 3 hybrid orbitals –called sigma bonds pi bonds: sp 2 hybrid orbitals

Hybrid Atomic Orbitals hybridbondingshaperotation bond sp 3 (  ) head-headtetrahedral free single sp 2 (  ) sidewaystriangularrigid double sp (  ) sidewayslinearrigidtriple

There are a Huge Number of Organic Molecules 100 new ones described every week It is estimated that there could be 5  different organic molecules

How Can So Many Molecules be Made From So Few Elements? different number of C atoms Functional groups (later) Isomers –iso means… Empirical formula- C 6 H 14 (molecular formula) Structural formula

Drawing Molecules As you can see already, drawing all these C-H bonds is tedious. We will use shortcuts most of the time. Condensed formula Line formula

Drawing Molecules on Paper Does not Show the 3-Dimensional Shape The geometry around each C atom is tetrahedral (sp 3 hybrid)

Hydrocarbons Hydrocarbon- Compounds which contain only carbon and hydrogen. Alkanes Alkenes Alkynes Cycloalkanes (Aromatics)

Alkanes meth-1 carbon eth- 2 carbons prop- 3 carbons but- 4 carbons pent- 5 carbons hex- 6 carbons hept- 7 carbons oct- 8 carbons non- 9 carbons dec- 10 carbons

Nomenclature Primary Secondary Tertiary Quaternary

6/15/04

IUPAC Nomenclature 1. Find the longest continuous carbon chain and use the name for the alkane with that number of carbon atoms. 2. Number the carbons in the longest continuous carbon chain from the end nearer the first R group. 3. Identify R groups by name. 4. Identify by number the carbon atom in the chain to which each substituent bonds. If the same substituent occurs more than once, identify each carbon number for that substituent, separate the numbers to commas, and use the appropriate prefix to identify how many occur in the compound. 5. Name the compound by listing the substituents preceded by a number and a hyphen, followed by the base name for the C chain. If more than one type R group, arrange in alphabetical order, ignoring prefixes except iso- and cyclo-. Connect all numbers and prefixes by hyphens.

R-groups by name

Cycloalkanes Whether the ring or chain is considered the parent compound depends on which is larger.

Functional Groups Functional group- An atom or group of atoms that imparts on a molecule a distinctive chemistry 1. Alkane- not considered a functional group 2. Alkyl halide 3. Alkene 4. Alkyne

Alkanes Only sigma bonds in molecules General formula C n H 2n+2 Molecular formula Structural formula Condensed formula Isomers- same formula, different structure functional isomers structural isomers

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Conformation of Molecules Important because of free rotation about the  - bond Eclipsed- Staggered- Important because of size of groups (can overlap)

Practice Conformation Problems Draw “all possible” Newman projections for the compound CH 3 CH 2 CH 2 CH 3 (butane)

Practice Conformation Problems What would the most stable conformation of the following molecule be?

Physical Properties of Alkanes 1. Solubility 2. mp/bp 3. Density