CHEM 430 – Structural Analysis of Organic Compounds

Spring 2014

IntroductionOur approach must differ depending on the type of work we are performing.

1. “Cold” analysis – the unknown organic is a complete unknown• Forensic chemistry• EPA methods and related analyses• Natural products taxonomy

In these cases, little if anything is known about the individual compounds – detective work must recreate the entire structure

2. Results of a synthetic experiment

In this case, the majority of the structure should be maintained, the goal is to analyze for and confirm changes

3. Characterization for the chemical literature – Assignments!

The analysis here is to confirm the author’s findings and serve as a benchmark for further work on the compound

IntroductionAll approaches will involve a general flow of information:

Methods in General Use

NMR Spectroscopy

NMR Spectroscopy

NMR Spectroscopy

NMR Spectroscopy

Mass Spectrometry

Vibrational Spectroscopy

Electronic Absorption Spectroscopy

Limitations (and grades)We can only see what our ‘shutter speed’ allows:

Technique Timescale

X-ray diffraction 10-18

UV 10-15

Visible 10-14

IR 10-13

ESR 10-4 to -8

NMR 10-1 to -9

Mössbauer 10-7

Experimental separation of isomers

102

Limitations (and grades)Can we ever achieve a fully secure structure (or why did I get it wrong?)?

Harrisonin

Heterocycles 1976, 5, 485.

J. Nat. Prod. 1997, 60, 822

Limitations (and grades)Can we ever achieve a fully secure structure (or why did I get it wrong?)?

J. Am. Chem. Soc. 1983, 105, 6312.

Tetrahedron Lett. 1992, 33, 3711J. Antibiotics 1986, 39, 1527

Limitations (and grades)Can we ever achieve a fully secure structure (or why did I get it wrong?)?

J. Org. Chem. 2001, 66, 8717.

Tetrahedron Lett. 2003, 44, 1203

Limitations (and grades)Can we ever achieve a fully secure structure (or why did I get it wrong?)?

J. Nat. Prod. 2000, 63, 1677.

J. Nat. Prod. 2003, 66, 716

Limitations (and grades)Can we ever achieve a fully secure structure (or why did I get it wrong?)?

J. Am. Chem. Soc. 2003, 125, 5296.Org. Lett. 2004, 6, 2607

Spirastrellolide

Limitations (and grades)Can we ever achieve a fully secure structure (or why did I get it wrong?)?

J. Nat. Prod. 2007, 70, 412.

J. Am. Chem. Soc. 2008, 130, 804

(+)-Neopeltolide

Welcome to CHEM 430

•Assumptions:• Working knowledge of general and organic

chemistry

• You have seen basic IR and NMR before

• Math skills permit solution of algebra and trigonometric problems and a rudimentary understanding of simple calculus