2.2: Reports

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First Report

Results (5 points)

Discuss the relative polarity of the two compounds and any other information learned about the compounds based on TLC analysis and acid/base extraction. Briefly describe the separation of the two components of your mixture. Describe the conditions used for the purification of each of the compounds including solvents used for recrystallization, temperatures, etc. Report the melting point and melting range of each purified compound and use this as well as TLC to assess the purity of the compounds.

Questions (5 points)

You will find out the structure of three compounds based on spectral information provided.

Final Report

Briefly describe the procedure used for the separation and purification of each of the two components of your unknown mixture. Include the conditions used for recrystallization as well as the % recovery from recrystallization. Discuss the evidence for purity based on TLC, melting point analysis and 1H NMR.

Identification of Acid Unknown

Present the spectral data obtained for your acid unknown. Tabulate the features of the 1H NMR spectrum. Locate in reference (2) above the table of known compounds with the functional groups of your acid unknown from the tables containing carboxylic acids or phenols. Tabulate in your report the names and structures of all compounds with melting points within 6° of your acid or base unknown. Eliminate as many structures as possible on the basis of your accumulated data (explain your reasoning). Describe the preparation of the derivative which you carried out to confirm the structure of your unknown.

Identification of Neutral Unknown

Present the spectral data obtained for your neutral unknown. For each spectrum, note such important experimental conditions as the solvent in which they were taken, and point out any features that are believed to be artifacts or impurities. For the 1H NMR spectrum, tabulate the features of the spectrum including integrations, multiplicities and coupling constants (where possible). For the 13C NMR spectrum, tabulate the peaks for the spectrum and note the solvent and position of the solvent peaks. Similarly present the results of the IR, GC-MS spectra in a tabular fashion. Describe in a general sense how each of the spectroscopic methods is most powerful for the analysis of unknowns, i.e. detection of certain elements, determination of molecular weight, determination of molecular formula, sensitivity to symmetry, electronic effects, etc.

Proceed to determine the molecular formula of your neutral unknown. Describe how each of the methods 1H NMR, 13C NMR, DEPT, gCOSY, HETCOR, elemental analysis and GC-MS can be valuable in this effort - and what their possible shortcomings can be. Ultimately your molecular formula must be compatible with all of these.

Deduce the structure of your neutral unknown. Discuss your reasoning in detail. Show on separate structures of your unknown your assignments of the proton and 13C resonances. Valuable insight concerning the interpretation of 1H NMR spectra may be obtained by inspection of molecular models of proposed structures. Make assignments of the prominent peaks in the IR spectrum. Also show how one or more of the fragmentation patterns in the mass spectrum are consistent with your structure. All of these methods will be valuable in determining the structure of your neutral unknown. If it was necessary to perform a functional group classification test, describe how this supports your proposed structure.

Submit to your TA each purified unknown so that its purity, mp, etc. can be checked.

Neutral Unknown Worksheet

Molecular Formula & MW	Elemental Anal. calc. obsd.	GC-MS Highest Ion Pattern	1H NMR integration	13C NMR # of lines

Unsaturation Number (# of double bonds or rings): ______
Unsaturated Functional Group	IR (cm-1)	13C NMR ppm	# of lines, #C	1H NMR ppm	#H	Unsaturation No. of FG

Remaining Molecular Symmetry:				Remaining Unsaturation:

1H NMR ( MHz, solvent)
label	d (ppm)	(multiplicity, #H, J values)

Subunits	Remaining 13C NMR subunits	Remaining subunits

Important Mass Spectrum Fragment Ions
m/e	(M+1) %	(M+2) %	Possible Assignments	m/e	(M+1) %	(M+2) %	Possible Assignments

Assembled Subunits	Reasoning

Structure of Unknown showing 1H NMR and 13C NMR assignments	Mass Spectral Fragmentation Mechanisms