General Approach
In this experiment, each student will be assigned an unknown number that corresponds to one of the compounds on the spectroscopy experiment master unknown list.  (See "Unknown Assignments" below for your specific lab section to find your assigned unknown number).  IR, NMR and mass spectral data for each of the unknowns is posted by unknown number under the "spectral data" section below.   Students will retrieve the spectral data posted on the website that corresponds to his or her assigned unknown.  Students will be required to read the experiment background and interpret the spectral data as outlined below.  During the spectroscopy workshops, students will be guided through the interpretation process.  Students who come prepared to the workshops will complete a significant part of the identification by the end of the workshop session. Attendance at one spectroscopy workshop will be required.  Spectroscopy workshops are scheduled for the week of November 26-30, 2007.  (See workshop schedule below). Upon identification of the unknown, students will be required to complete the spectroscopy worksheet.  There is no pre-lab, quiz, notebook or technique grade for this experiment.  The overall experiment grade will be determined based on attendance at one workshop and the spectroscopy worksheet.  The worksheet for this experiment is due the week of December 3 at 5:00pm on the day of your regularly scheduled lab.  The worksheet must be submitted on BB through the laboratory link for the course in the same way you have submitted other post lab assignments.

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Finding your Unknown Number and Retrieving Your Spectral Data

Monday,  8:00-10:50am (Lab A)	Wednesday 8:00-10:50am  (Lab E)	Thursday 3:00-5:50pm (Lab H)
Monday 11:00am-1:50pm  (Lab B)	Wednesday  11:00am-1:50pm (Lab F)	Friday 8:00-10:50am (Lab I)
Tuesday  12:30-3:20pm  (Lab C)	Wednesday  6:00-8:50pm (Lab G)	Friday 1:00am-1:50pm (Lab J)
Tuesday 3:30-6:20pm (Lab D)	Thursday  12:00-2:50pm (Lab BS)	Friday 2:00-4:50pm (Lab K)

Spectral Data Master Unkown List  (pdf)
1-50	101-150
51-100	151-200
201-250

Review the Spectroscopy workshop schedule below and plan to attend one of the sessions.  The earlier in the week the better.  Bring all your spectral data either in printed or electronic format and a copy of the master list of unknown compounds (above in table) to the workshop. Also bring your lab notebook and your laptop.

Spectroscopy Workshop Schedule
Monday   11/26    9:30-11:00am          OB110	Monday   11/26    4:00-5:30pm          OB218
Tuesday   11/27     11:00-12:30pm          OB102A	Wednesday  11/28   12:30-2:00pm      OB110
Thursday    11/29     4:30-6:00pm       CL208	Friday   11/30     9:30-11:00am           OB110

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The process of spectral analysis of an unknown compound is an iterative process.  An iterative process is one that approaches a solution to a problem through a series of approximations, starting with some basic information.  The basic information is used to narrow the possible solutions, then the data is analyzed in finer and finer detail until a complete solution is reached.   In this experiment, the basic information is obtained from a crude analysis of the spectral data.  Successive analyses of each piece of spectral data (IR, then NMR, then mass spectrum, then back to NMR) provides information that allows for elimination of compounds from the master list until only a few compounds remain as options.  The final identification is done by doing a detailed analysis of the NMR spectrum and relating the NMR spectrum to the few compounds that remain from the master list.  The process requires that students flip between spectral information and the structures of unknown compounds on the master list.  Use the Merck Index, Chemfinder, the Handbook of Chemistry and Physics or other resources to locate the structures of each of the compounds on the list as you work through this iterative method.  You may (and should) work with your classmates to collect the structures.

Interpreting the IR Spectrum
The IR spectrum of your unknown will allow you to identify specific functional groups that are present in your compound, and those functional groups that are not present.  Analysis of the IR spectrum will allow you to eliminate many of the compounds on the master unknown list.  Use the step by step process outlined below to interpret the IR spectrum  of your unknown.

Step 1	Identify all the major peaks in the spectrum between 3600cm-1 and 1500cm-1 (+/- 100cm-1).  Label the peaks on the spectrum as 1,2,3 etc and prepare a table in your notebook with four columns with the following headings:  Peak Number, Absorbance Range, Absorbance Intensity, Bond Type.  Label the Table as Analysis of IR Spectrum for Unknown # ___.  Enter all peak numbers in the "Peak Number" column, their corresponding absorbance range in the "Absorbance Range column, and the absorbance intensity (Strong =50% of scale or more; Medium 25-505 of scale; Weak = less than 25% of scale) in the "Absorbance Intensity" column.
Step 2	Is there a peak between 1650-1850cm-1 and  3600-3200cm-1?  If  yes go to Step 3. If no go to Step 5.
Step 3	Is the peak between 3600-3200cm-1 broad and intense?  If no, go to Step 4.  If yes, the compound probably contains one of the following functional groups or functional group combinations. 1)  Carboxylic acid 2) Ketone and alcohol or phenol 3) Aldehyde and alcohol or phenol 4) Ester and alcohol or phenol 4) Alkene and Alcohol or phenol 5)  Phenol List these possible functional groups in the table under the "Bond Type" column next their corresponding peaks listed in the table.
Step 4	Is the peak between 3600-3200cm-1 sharp and medium to weak in intensity? If yes, the compound probably contains one of the following functional groups or functional group combinations: 1) Secondary amide (if only one peak between 3600-3200cm-1) primary amide (if two peaks between 3600-3200cm-1) or 2) Ketone and amine or 3) Aldehyde and Amine List these possible functional groups in the table under the "Bond Type" column next their corresponding peaks listed in the table.
Step 5	Is there a peak between 1650-1850cm-1 ?  If no, go to Step 6.  If yes, the compound contains one of the following carbonyl or C=C containing functional groups: 1) ester 2) ketone 3) aldehyde 4) tertiary amide 5) alkene (~1660cm-1) 6) aromatic (~1450 and 1600cm-1) List these possible functional groups in the table under the "Bond Type" column next their corresponding peaks listed in the table.
Step 6	Is there a  peak between 3600-3200cm-1 ?  If no, go to Step 7.  If yes, the compound contains one of the following functional groups: 1) Alcohol (if the peak is broad and strong in intensity) 2) Amine (if the peak is sharp and medium in intensity) List these possible functional groups in the table under the "Bond Type" column next their corresponding peaks listed in the table.
Step 7	The compound contains one or more of the following functional groups: 1) Alkane 2) Ether 3) Alkyl Halide List these possible functional groups in the table under the "Bond Type" column next their corresponding peaks listed in the table.
Step 8	Review the list of bond type/functional groups in the table you completed.  Cross out all compounds on the master unknown compound list that contain functional groups that are not on your list.  Proceed to the crude analysis of the NMR spectrum of your unknown.

Crude Analysis and Interpretation of the NMR Spectrum
Crude analysis of the NMR spectrum of your unknown will allow you to identify some general structural characteristics of your unknown. Through crude analysis of the NMR spectrum, additional compounds can be eliminated from the master list.    Use the step by step process outlined below to do a preliminary interpretion of  the NMR spectrum  of your unknown.

Step 1	Identify all the peaks in the NMR spectrum.  Label the peaks in the spectrum as 1,2,3 etc and prepare a table in your notebook with four columns with the following headings:  Peak Number, Chemical Shift, Multiplicity,  and Proton Type.  Label the Table as Analysis of NMR Spectrum for Unknown # ___.  Enter all peak numbers in the "Peak Number" column, their corresponding exact chemical shift range in the "Chemical Shift" column, and the multiplicity (singlet, doublet, etc..) in the "multiplicity" column.  Use the information in Table 5 of the background reading to identify the specific proton type.  Fill this information into the table under "proton type" for each peak.
Step 2	Are there any peaks in the range of 6.5-8.0 ppm?  (aromatic region)  If yes, your compound contains aromatic protons, likely a benzene or related aromatic ring.   Eliminate all remaining compounds on the master unknown compound list that do not contain an aromatic ring.  If no, your compound does not contain a benzene or related aromatic ringEliminate all compounds on the list that do contain an aromatic ring.
Step 3	Are there any peaks in the region between 10-12ppm?  If yes, your compound contains a carboxylic acid or aldehyde.  Eliminate any remaining compounds on the master unknown compound list that do not contain one of these functional groups.  If no, your compound does not contain an aldehyde or carboxylic acid.  Eliminate any remaining compounds on the master unknown compound list that do contain one of these functional groups.

Interpreting  the Mass Spectrum
The mass spectrum provides information about the molecular weight of the unknown and whether the compound contains a bromine or chlorine atom.  Coupled with the crude NMR spectral analysis and the IR spectral analysis, interpretation of the mass spectrum of the unknown will limit the number of possible unknowns that are consistent with all of the spectral data to only a few compounds.

Step 1	Prepare a section in your notebook for recording data from the mass spectral analysis.   Label the section in the notebook as Mass Spectral Analysis of Unknown # ___
Step 2	Identify the parent peak (M+) in the spectrum  and record the m/z value for the parent peak.  This m/z value  corresponds to the molecular weight of the unknown compound.
Step 3	Look for M++2 peaks that are at least 20-25% relative abundance (intensity).  No M++2 peak indicates that there is no chlorine or bromine atom in the unknown compound.  The presence of an M++2 peak that is ~25%  the relative intensity of the M+ peak indicates that the unknown contains a chlorine atom.  If the compound contains a chlorine, review the remaining compounds on the list and eliminate any compounds that do not contain a chlorine. If the compound does not contain a chlorine, eliminate any compoundson the list that do contain a chlorine.
Step 4	The presence of an M++2 peak that is ~50%  the relative intensity of the M+ peak indicates that the unknown contains a bromine atom.   If the compound contains a bromine, eliminate any compounds remaining on the list that do not contain a bromine.  If the compound does not contain a bromine, eliminate any compounds from the list that do contain a bromine atom.
Step 5	Review the compounds on the list and using Cherm finder or another resource, find the molecular weights of the remaining compounds on the list.  Eliminate any compounds on the list that do not have molecular weights consistent the m/z value of the parent peak in the spectrum.

Detailed Analysis of the NMR Spectrum
After completion of the mass spectral interpretation, the number of compounds remaining on the list may be 8 or 9 possible compounds, or there may be only one compound remaining.  Regardless of the number of compounds remaining on the list, a detailed NMR ananlysis must be done on the remianing compound(s) (even if it is only one compound).  The detailed NMR analysis involves the following steps, outlined below.

Step 1	Set up a new section in the notebook labeled Detailed Ananlysis of the NMR Spectrum of Unknown # ___.  Draw the structures of all of the remaining compounds, drawing out all of the hydrogen atoms in each structure.
Step 2	In your notebook, set up a table for each structure that you drew that lists the different types of protons in the structure, the predicted chemical shift of each proton or group of protons, and the predicted multiplicity of each proton/group of protons.
Step 3	In your notebook, sketch a predicted NMR spectrum from the data compiled in each table for each remaining compound.
Step 4	If the sketched spectrum contains extra peaks, peaks with multiplicities different from the provided spectrum or has peaks missing, it is not consistent with the unknown spectrum.   Compounds whose sketched spectrum is not consistent with the provided spectrum can be eliminated as possibilities.
Step 5	The compound whose sketched spectrum correlates the best with the provided spectrum and is completely consistent with the provided spectrum corresponds to the identity of the unknown.

An example of a detailed NMR spectral analysis is given below.  Assume that after the IR, crude NMR and mass spectral analysis, that only two compounds remain on the list, 3-hydroxy-2-butanone and ethyl acetate. The structures of each of these compounds are drawn (shown below) and the protons (hydrogens) in each structure are explicitly drawn.  The hydrogens in each strucutre are grouped as equivalent, non-equivalent and are labeled in the structure.  The chemical shifts of these protons  are predicted using the information in Table 5 from the background reading.  The multiplicities are also predicted based on identifying the neighboring hydrogens.  The information about each of these hydrogens is tabluated and used to sketch the spectrum of each compound.  The sketched spectra are compared with the provided spectrum.  The sketched spectrum from ethyl acetate is more consistent with the provided spectrum than 3-hydroxy-2-butanone. 

Compounds	Proton Types	Sketched Spectra
ethyl acetate	Proton Multiplicity Chemical Shift Range Ha singlet 1.5-2.5 ppm Hb quartet 2.5-4.5 ppm Hc triplet 0-1.5 ppm
3-hydroxy-2-butanone	Proton Multiplicity Chemical Shift Range Ha singlet 1.5-2.5 ppm Hb broad s anywhere Hc quartet 2.5-4.5ppm Hd doublet 0-1.5ppm
Provided Spectrum

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