Identifying an Unknown Substance using Infrared Spectroscopy (IR), Carbon-13 Nuclear Magnetic Resonance ( 13 C NMR), and Proton Nuclear Magnetic

Transcription

1 Identifying an Unknown Substance using Infrared Spectroscopy (I), arbon-13 Nuclear Magnetic esonance ( 13 NM), and Proton Nuclear Magnetic esonance ( 1 NM)

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3 Identifying an Unknown Substance using Infrared Spectroscopy (I), arbon-13 Nuclear Magnetic esonance ( 13 NM), and Proton Nuclear Magnetic esonance ( 1 NM) y: Veronica Partridge

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5 Table of ontents v Table of ontents Table of ontents... v Introduction... vii Symbols used in this manual... vii What is this experiment about... viii ow are the points distributed... viii Infrared Spectroscopy (I)... 3 What is I used for... 3 Example of an I spectra... 3 Table of I values... 4 Identifying Functional Groups using I... 5 arbon-13 Nuclear Magnetic esonance ( 13 NM)... 9 What is 13 NM used for... 9 Example of a 13 NM spectra... 9 Table of 13 NM values Identifying Function Groups from 13 NM peaks Labeling arbons using 13 NM Proton Nuclear Magnetic esonance ( 1 NM) What is 1 NM used for Example of a 1 NM spectra Table of 1 NM values Identifying 1 NM peaks Labeling Protons using 1 NM Drawing a Structure using 1 NM Identifying the Unknown alculating the degree of unsaturation Drawing the structure Putting the data together ommon Problems The Values for I, 13 NM, or 1 NM do not Match up Perfectly There is only one Signal on the 1 NM spectra There is a reak in my 1 NM spectra There is no Split on a peak for 1 NM spectra I can t see how many splits there are in the 1 NM spectra... 33

6 vi Identifying an Unknown Substance using I, 13 NM, & 1 NM The peak has 1 next to it but no peak Does this atom affect the degree of unsaturation? Index... 35

7 Introduction vii Introduction This manual is for students in the Organic hemistry I Lab who have at least a beginners understanding of organic chemistry. This manual is meant to guide the student through the identification of an unknown substance using Infrared Spectroscopy (I), arbon-13 Nuclear Magnetic esonance ( 13 NM), and Proton Nuclear Magnetic esonance ( 1 NM) This manual is organized by each part of the experiment: 1. Infrared Spectroscopy (I) 2. arbon-13 Nuclear Magnetic esonance ( 13 NM) 3. Proton Nuclear Magnetic esonance ( 1 NM) 4. Identifying the Unknown It also includes a section for common problems when doing this experiment. NOTE The data used to give an example on how to identify an unknown substance will not be the same as the data given to you, so you will not get the same compound as shown in this manual. The data given to you will be unique to that student and no two students will have the same data or substance. Symbols used in this manual Table 1 shows the symbols used in this manual and what they mean. Table 1 Symbol Means Triple ond = Double ond - Single ond > onnected to a arbon Skeleton - onnected to any Other Molecule 1 Primary 2 Secondary 3 Tertiary -X onnected to a alogen (F, l, r, I, At) π Double or Triple bond

8 viii What is this experiment about Identifying an Unknown Substance using I, 13 NM, & 1 NM In this experiment you will be using Infrared Spectroscopy, arbon-13 Nuclear Magnetic esonance, and Proton Nuclear Magnetic esonance to identify an unknown substance. While doing this experiment, please keep in mind that due to acidic functional groups your I, 13 NM, or 1 NM values may be somewhat off. ow are the points distributed In order to get the full 20 points on this experiment you must Identify the peaks in the I spectra and what functional groups they can relate to. (2 pts.) Identify the peaks in NM and how that shows what the carbon atom is attached to. (4 pts.) o Label the carbons with which peak they relate to. Identify the peaks in NM and how it shows how many hydrogen atoms are attached to a carbon atom. (10 pts.) o Label the hydrogen with which peak they relate to. o reate fragments of the compound using the spectral data. Identify the compound. (4 pts.) o Write the number of the unknown substance at the top of your paper. o Draw the structure. All hydrogen must be drawn out. o Find the degree of unsaturation. List a table with all possible rings and π bonds.

9 Infrared Spectroscopy (I)

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11 arbon-13 Nuclear Magnetic esonance 3 Infrared Spectroscopy (I) In this section you will use the I chart and table to identify the functional groups of an unknown substance. This section Explains what I is for Gives an example of an I spectra Gives a table of I values Shows how to identify functional groups using I What is I used for I is used to identify any functional groups the organic substance may have which can help predict how the compound will react with other substances. Example of an I spectra Figure 1 is the I spectra of an unknown substance. Figure 1

12 4 Identifying an Unknown Substance using I, 13 NM, & 1 NM Table of I values Table 2 below shows what values go with the functional groups. Table 2 ompounds Functionl Group Terminal Alkyne Fragments Giving I Signals Alkynyl ( ) Typical I Signals (cm -1 ) Alkynyl ydrogen ( -) ~3300 Internal Alkyne Alkynyl ( ) Alkene Alkenyl (=) Aldehyde arbonyl (>=O) Ketone arbonyl (>=O) arboxylic Acid Ester Amide arbonyl (>=O) ydroxy (-O-) arbonyl (>=O) Alkoxy (-O 3 ) arbonyl (>=O) Amino (-N 2 ) 1 Amine Primary Amino (-N 2 ) -N 2 Amine Secondary Amino (>N-) -N 3 Amine Tertiary Amino (>N-) (2 signals) (1 signal) No signal Alcohol -N ydroxy (-O-) Phenol ydroxy (-O-) Ether Alkoxy (-O-) Aromatic Aromatic (-) Phenyl (=) ~

13 arbon-13 Nuclear Magnetic esonance 5 Identifying Functional Groups using I In order to identify functional groups using I you will need to refer to the I spectra given in the experiment hand out and the table on the previous page. Follow the steps below to identify the functional groups in an unknown substance using I: 1. Eliminate impossible functional groups by looking at the molecular formula on the handout. 2. Look for distinct functional group signals like an alcohol or an amine. 3. Label as many peaks as you can. 4. List all possibilities for the peak. 5. ompare the possibilities of the functional groups from the I to the possibilities of the functional groups from the 13 NM and 1 NM. elow is an example for identifying functional groups using the I spectra The possibilities for this unknown based on Figure 2 are The letter A could be an alcohol, phenol, or carboxylic acid The letter could be a ketone, phenyl, or carboxylic acid The letter could be an ether or normal carbon A Figure 2

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15 arbon-13 Nuclear Magnetic esonance ( 13 NM)

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17 arbon-13 Nuclear Magnetic esonance 9 arbon-13 Nuclear Magnetic esonance ( 13 NM) In this section you will use the 13 NM spectra and table to identify the functional groups of an unknown substance and label carbons. This section Explains what 13 NM is for Gives an example of an 13 NM spectra Gives a table of 13 NM values Shows how to identify functional groups using 13 NM Shows how to label carbons using a 13 NM spectra What is 13 NM used for 13 NM is used to determine how the carbons in a substance are put together and how close they are to other functional groups. Example of a 13 NM spectra Figure 3 is the 13 NM spectra for an unknown substance. Figure 3

18 10 Identifying an Unknown Substance using I, 13 NM, & 1 NM Table of 13 NM values Table 3 shows what values go with what type of carbon. Table 3 Type of carbon Atom Structure hemical Shift Value (ppm) 1 Alkyl Alkyl Alkyl Alkyl halide Amine (1, 2, and 3 ) Alcohol Ether Alkyne (Terminal and Internal) Alkene Aryl (Phenyl) Nitrile Amide arboxylic acid Ester Aldehyde Ketone

19 arbon-13 Nuclear Magnetic esonance 11 Identifying Function Groups from 13 NM peaks In order to identify functional groups using 13 NM you will need to refer to the 13 NM spectra given in the experiment hand out and the table on the previous page. Follow the steps below to identify the functional groups in an unknown substance using 13 NM: 1. Eliminate impossible functional groups by looking at the molecular formula. 2. Look for distinct functional group signals like an aldehyde or a ketone. 3. Label all the peaks with a number. 4. List all possibilities for the peak. 5. ompare the possibilities of the functional groups from the 13 NM to the possibilities of the functional groups from the I and 1 NM. elow is an example for identifying function groups using 13 NM The possibilities for this unknown based on Figure 4 and the possibilities of the I spectra are The number 1 could be a carboxylic acid The number 2 could be an outside carbon on a aryl ring The number 3 could be an aryl The number 4 could be an aryl The number 5 could be an aryl The number 6 could be a 3 Alkyl The number 7 could be a 2 Alkyl The number 8 could be a 1 Alkyl Figure 4

20 12 Identifying an Unknown Substance using I, 13 NM, & 1 NM Labeling arbons using 13 NM In order to label carbons using 13 NM you will need to refer to the 13 NM spectra given in the experiment hand out and the table on the previous page (10). You will need to identify the functional groups before labeling. Follow the steps below to label the carbons with what signal they show: 1. Identify the functional groups of the substance. 2. Label the 13 NM spectra with numbers. 3. Draw the structures of each functional group. 4. Label the carbons in the structures with the letter or number that goes with the signal. 5. Label the carbons in the final structure after you identify it. elow is an example for labeling carbons using 13 NM where the orange numbers represent carboms Figure 5 uses the information from Figure 4 to create the structures you see. O 1 O Figure Figure 4

21 Proton Nuclear Magnetic esonance ( 1 NM)

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23 Proton Nuclear Magnetic resonance 15 Proton Nuclear Magnetic esonance ( 1 NM) In this section you will use the 1 NM spectra and table to identify the functional groups of an unknown substance, figure out how a structure is put together, and label hydrogen (protons) with the peak they show on a 1 NM spectra. This section Explains what 1 NM is for Gives an example of a 1 NM spectra Gives a table of 1 NM values Shows how to identify functional groups using 1 NM Shows how to predict a structure using 1 NM Shows how to label hydrogen using a 1 NM spectra What is 1 NM used for 1 NM is used to determine how the substance is put together. It is useful to help figure out which carbons have protons and how many protons they have. This is helpful in putting together parts of a structure of a substance into the final structure. Proton signals are split when there are nearby protons which make the signal appear to have bumps. The number of bumps is equal to the number of nearby hydrogen + one. The number above the signal is the number of unique protons that are connected to a single carbon. Example of a 1 NM spectra Figure 6 is the 1 NM spectra of an unknown substance. Figure 6

24 16 Identifying an Unknown Substance using I, 13 NM, & 1 NM Table of 1 NM values Table 4 shows what values go with what type of proton. Table 4 Type of proton Structure hemical Shift Value (ppm) Alkyl 2 Alkyl Alkyl Allylic (alkene) Ketone enzylic Acetylenic Alkyl iodide Ether Alcohol Alkyl bromide Alkyl chloride Vinylic (a) Vinylic (b) Aromatic Aldehyde Alcohol hydroxyl Amino Phenolic arboxylic 10-13

25 Proton Nuclear Magnetic resonance 17 Identifying 1 NM peaks In order to identify functional groups using 1 NM you will need to refer to the 1 NM spectra given in the experiment hand out and the table on the previous page. Follow the steps below to identify the functional groups in an unknown substance using 1 NM: 1. Eliminate impossible functional groups by looking at the molecular formula. 2. Look for distinct functional group signals like a carboxylic. 3. Label all the peaks with a letter. 4. List all possibilities for the peak. 5. ompare the possibilities of the functional groups from the 1 NM to the possibilities of the functional groups from the I and 13 NM. elow is an example for identifying function groups using 1 NM The possibilities for this unknown based on Figure 7 and the possibilities of the I spectra and 13 NM are The letter A could be a carboxylic acid The letter could be an aromatic The letter could be an aromatic outside The letter D could be a 2 Alkyl The letter E could be a 3 Alkyl The letter F could be a 1 Alkyl F A D E Figure 7

26 18 Identifying an Unknown Substance using I, 13 NM, & 1 NM Labeling Protons using 1 NM In order to label protons using 1 NM you will need to refer to the 1 NM spectra given in the experiment hand out and the table on the previous page (16). You will need to identify the functional groups before you can label the protons. Follow the steps below to label protons in an unknown substance using 1 NM: 1. Identify the functional groups of the substance. 2. Label the 1 NM spectra with letters. 3. Draw the structures of each functional group. 4. Label the protons in the structures with the letter or number that goes with the signal. 5. Label the protons in the final structure after you identify it. elow is an example for labeling protons using 1 NM where the orange letters are protons Figure 8 uses the information from Figure 7 to create the structures you see. O OA F F F E E D Figure 8 F D E A Figure 7

27 Proton Nuclear Magnetic resonance 19 Drawing a Structure using 1 NM In order to draw a structure using 1 NM you will need to refer to the 1 NM spectra given in the experiment hand out and the table on the previous page (16). When drawing structures using 1 NM it is important to know that The number of splits or bumps is equal to the number of nearby protons + one. The number near the peak is the number of unique protons on the carbon. o Equivalent protons will only show as one signal such as in aromatic structures. Follow the steps below to draw a structure using 1 NM: 1. Identify the functional groups of the unknown. 2. Label all the peaks with a letter. 3. Label the hydrogen with the peak they show. 4. Use the number of hydrogen by the peak to start the structure. 5. Use the number of splits" to put the pieces together. elow is an example for drawing a structure using 1 NM with the orange letters representing hydrogen Figure 9 uses the information from Figure 7 to create the structure you see. F E D F F E O OA Figure 9 F D E A Figure 7

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29 Identifying the Unknown

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31 Identifying the Unknown 23 Identifying the Unknown In this section you will put the information gathered from the previous sections and identify the unknown. You must have already completed the previous sections before you can do this section. This section Shows how to calculate the degree of unsaturation Shows how to draw the structure Explains how to put the data together alculating the degree of unsaturation The degree of unsaturation has to do with how many rings and/or double (π) bonds a substance has. The rings and π bonds only relate to carbons. The formula for calculating the degree of unsaturation is below. Degree of Unsaturation = 2+2+N-X- 2 =Number of arbon N=Number of Nitrogen X=Number of alogens (F, l, r, I) =Number of ydrogen NOTE The numbers used here are the numbers given from the molecular formula on the experiment handout. Follow the steps below to calculate the degree of unsaturation: 1. Look at the molecular formula. 2. Times the number of carbon by two. 3. Add two. 4. Add the number of nitrogen. 5. Subtract the number of halogens. 6. Subtract the number of hydrogen. 7. Divide by two. 8. Figure out the number of possible rings or π bonds.

32 24 Identifying an Unknown Substance using I, 13 NM, & 1 NM elow is an example on how to calculate the degree of unsaturation The molecular formula used for this example is O 2. 2(10) = 5 The degree of unsaturation for this substance is 5. Follow the steps below to calculate the number of rings or π bonds in a substance: 1. alculate the degree of unsaturation. 2. Make a table. 3. List the possible number of rings. 4. List the possible number of double bonds. 5. List the possible number of triple bonds. NOTE ings count as one degree of unsaturation. Double bonds count as one degree of unsaturation. Triple bonds count as two degrees of unsaturation. elow is an example of how to calculate the number of rings or π bonds in a substance The molecular formula used for this example is O 2. The degree of unsaturation for this substance is 5. Table 5 Table 5 shows the possible combination based on the degree of unsaturation. Table 5 Degree of unsaturation Possible combinations of rings or π bonds 5 Number of ings Number of double bonds Number of triple bonds

33 Identifying the Unknown 25 Drawing the structure This section is to show you how to draw the structure of the unknown substance based on the I, 13 NM, and 1 NM spectra. efore attempting to draw the structure make sure You have identified the functional groups. You have drawn the fragments of the structure using the 13 NM and 1 NM spectra. Follow the steps below to draw the structure of the unknown substance: 1. Identify the functional groups. 2. Draw the fragments of the structure using the 13 NM and 1 NM spectra. 3. Piece the fragments together using the 1 NM spectra. 4. Draw the final structure with all hydrogen. elow is an example on how to draw the structure of an unknown substance The functional groups in this unknown are a carboxylic acid and an aromatic ring. Figure 10 shows the fragments to be put together based off of the 13 NM and 1 NM spectra. O O Figure 10 Figure 11 shows the final structure with all hydrogen showing. O O Figure 11

34 26 Identifying an Unknown Substance using I, 13 NM, & 1 NM Putting the data together This section is to help you put all your data together. To get full points you should be sure to include all information listed in this section. Follow the steps below to put your data together: 1. Write the number of your unknown at the top of the paper. 2. Find the degree of unsaturation. 3. Identify the functional groups using I, 13 NM, and 1 NM. a. Label the I with what function groups they are. 4. Draw the structure with all hydrogen drawn out. a. Draw the fragments using the 1 NM data with labeled protons. 5. Draw the final structure. a. Label the hydrogen and carbon with the peaks that they show on the spectra. elow is an example on how to put your data together and how you should set up your lab report 1. Unknown 070j 2. The molecular formula used for this example is O 2. 2(10) = 5 The degree of unsaturation for this substance is 5. Degree of unsaturation Possible combinations of rings or π bonds 5 Number of ings Number of double bonds Number of triple bonds

35 Identifying the Unknown A and in are signals from a carboxylic acid. A

36 28 Identifying an Unknown Substance using I, 13 NM, & 1 NM O O F OA O O F F F E E D 4. The fragments below are to be combined using the 1 NM spectra This is the final structure with hydrogen showing: A D E

37 Identifying the Unknown F F F 7 E E 8 D 1 OA O = F 5. The structure below is labeled using the 13 NM spectra and the 1 NM spectra A D E

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39 ommon Problems

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41 ommon Problems 33 ommon Problems In this section are common problems when trying to identify the unknown substance. The Values for I, 13 NM, or 1 NM do not Match up Perfectly If the values are not spot on do not fret. This is likely due to an impurity of sorts. So long as the values are in the general area and you can prove that the substance is without a doubt the compound you found it to be it will be fine. There can be a lot of shifting due to highly acidic functional groups such as carboxylic acids. There is only one Signal on the 1 NM spectra This is how substances that are symmetrical show up. This is also known as the hydrogen all being equal For example benzene will only have one peak on the 1 NM spectra because it is completely symmetrical. There is a reak in my 1 NM spectra This is because there are no peaks between the number last shown and the number listed after it. There is no Split on a peak for 1 NM spectra This means that all the hydrogen on the nearby carbon are equal or symmetrical. I can t see how many splits there are in the 1 NM spectra This is because there are more than three protons on a nearby carbon. The peak has 1 next to it but no peak This means that the nearby carbon has no hydrogen. Does this atom affect the degree of unsaturation? The only atoms that affect the degree of unsaturation are carbon, hydrogen, halogen, and nitrogen.

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43 Index 35 Index 13 NM, 7, 9, 10, 11 1 NM, 15, 16, 17 example, 3, 9, 11, 15, 17, 18, 19, 33 Example, 3, 9, 15 Identifying, 5, 11, 17, 23 I, viii, 3, 4, 5, 11, 17, 18, 19 NOTE, vii, 23, 24 Problems, 33 unsaturation, viii, 23, 24, 26 values, 4, 11, 17