IR & 3C NMR Unknown Your mission is to determine the structure of your unknown f
ID: 546623 • Letter: I
Question
IR & 3C NMR Unknown Your mission is to determine the structure of your unknown from the molecular formula, IR and 1BC NMR spectra. Assign all of your 13C NMR absorptions. You want to know which resonances correspond to which parts of the product's structure. The best way to do this is to draw a picture of the molecule right on the NMR spectrum then label each C on the molecule with a letter (Ca, Cb, Ce...). Use these same labels right on the spectrum. Also tabulate your NMR data (chemical shift&interpretation;). Identify as many IR absorptions as you can. ALL WORK MUST BE SHOWN! Use the space below and the back. Draw the final structure in the box below. Unknown # Structure:Explanation / Answer
The molecular formula of the compound is C5H10O2.
Based on IR spectrum:
Peaks in the range 2500-3300 cm-1 account for the C-H stretching. Broad band indicates the presence of O-H stretching, hydrogen bonded (part of carboxylic acid)
Peak at 1712 cm-1 account for the C=O stretching of carboxylic acid/ester
Peaks at 1500, 1450, 1300, 1200 cm-1 account for O-H bending, C-O stretching, C-H bending
Peak at 950 cm-1 account for O-H bending
Based on 13C NMR spectrum:
In the above spectrum, there are five peaks which indicate that are no carbon with the same enviroment.There are 5 different carbons. The first peak (C1) at 181 ppm, it is within the range 155 to 185 therefore, the carbon type could be either RCOOR or RCOOH.The second peak (C2) is at 34 ppm, third peak (C3) at 26.9 ppm and fourth peak (C4) is at 22.3 ppm and the fifth peak (C5) at 13.7 ppm, which are within the range 15 to 55ppm. These indicate the carbons are SP3.
Based on IR and 13C-NMR, the possible structure of the unknown could be:
5 4 3 2 1
CH3-CH2-CH2-CH2-COOH ---------- pentanoic acid
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