Column: IR Spectral Interpretation Workshop

The C=O Bond, Part VIII: Review

Nov 01, 2018

By Brian C. Smith

We review the group wavenumbers of the many carbonyl-containing functional groups we have examined this year and discuss how to distinguish these functional groups from each other.

The C=O Bond, Part VII: Aromatic Esters, Organic Carbonates, and More of the Rule of Three

Sep 01, 2018

By Brian C. Smith

Aromatic esters follow the ester Rule of Three, but each of these three peak positions is different for saturated and aromatic esters, which makes them easy to distinguish. Organic carbonates are structurally similar to esters and follow their own Rule of Three.

The C=O Bond, Part VI: Esters and the Rule of Three

Jul 01, 2018

By Brian C. Smith

Esters are a common and economically important functional group made by reacting an alcohol and a carboxylic acid.

The Carbonyl Group, Part V: Carboxylates—Coming Clean

May 01, 2018

By Brian C. Smith

Carboxylates are made by reacting carboxylic acids with strong bases such as inorganic hydroxides. Carboxylates contain two unique carbon–oxygen “bond and half” linkages that coordinate with a metal ion to give two strong infrared peaks, which make them easy to see.

The C=O Bond, Part IV: Acid Anhydrides

Mar 01, 2018

By Brian C. Smith

Acid anhydrides are unique in that they have two carbonyl groups in them. The intensity and position of their IR peaks can be used to determine which of the four types of anhydride exist in a sample.

IR Spectral Interpretation Workshop Quizes


Quiz 18: Your latest interpretation problem is shown in the figure presented in this quiz. Using what you have learned from the September installment of "IR Spectral Interpretation Workshop" and previous columns, determine the functional groups present from the spectrum given, and try to discover the chemical structure of this compound. Remember that not all peaks will be useful in the structural determination. Take the quiz!

Quiz 17: Your latest interpretation problem is shown in the figure presented in this quiz. Using what you have learned from the July installment of "IR Spectral Interpretation Workshop" and previous columns, determine the functional groups present from the spectrum given, and try to discover the chemical structure of this compound. Remember that not all peaks will be useful in the structural determination. Take the quiz!

Quiz 16: Your latest interpretation problem is shown in the figure presented in this quiz. Using what you have learned from the March installment of "IR Spectral Interpretation Workshop" and previous columns, determine the functional groups present from the spectrum given, and try to discover the chemical structure of this compound. Remember that not all peaks will be useful in the structural determination. Take the quiz!

Quiz 15: Your latest interpretation problem is shown in the figure presented in this quiz. Using what you have learned from the January installment of "IR Spectral Interpretation Workshop" and previous columns, determine the functional groups present from the spectrum given, and try to discover the chemical structure of this compound. Remember that the inclusion of a peak position in the table does not necessarily mean it will be useful in the structure determination. Take the quiz!

Quiz 14: Your latest interpretation problem is shown in the figure presented in this quiz. Using what you have learned from the November installment of "IR Spectral Interpretation Workshop" and previous columns, determine the functional groups present from the spectrum given, and try to discover the chemical structure of this compound. Take the quiz!

Quiz 13: Your latest interpretation problem is shown in the figure presented here. Using what you have learned from the September installment of "IR Spectral Interpretation Workshop" and previous columns, do your best to assign the peaks in this spectrum, determine the functional groups present, and determine the chemical structure of the molecule that gave rise to this spectrum. Take the quiz!

Quiz 12: Your latest interpretation problem is shown in the figure presented here. Using what you have learned from the July installment of "IR Spectral Interpretation Workshop" and previous columns, do your best to assign the peaks in this spectrum, determine the functional groups present, and determine the chemical structure of the molecule that gave rise to this spectrum. Ignore the peaks with an x through them. Take the quiz!

Quiz 11: Your latest interpretation problem is shown in the figure presented here. Using the information provided here and what you have learned from previous columns, do your best to assign the peaks in the spectrum shown in the figure and table, determine the functional groups present, and determine the chemical structure of the molecule that gave rise to this spectrum. Take the quiz!

Quiz 10: Your latest interpretation problem is shown in the figure presented here. Using the information provided here and what you have learned from previous columns, try to determine the complete chemical structure of this pure compound. At minimum try to determine whether this is an alcohol, and if it is, what type it is. Here's a hint: To make life easier, assume the peak at 2872 is at 2855. Take the quiz!

Quiz 9: The infrared spectrum for your next interpretation exercise is shown in the figure presented here. Using the information provided here and what you have learned from previous columns, try to determine the complete chemical structure of this pure compound. At minimum try to determine whether this is an alcohol, and if it is, what type it is. Here's a hint: Assume the 2965 and 2938 peaks are the same size. They might not appear so due to a plotting error. Take the quiz!

Quiz 8: Your latest interpretation problem is shown in the figure presented here. In this problem use what you learned from this column to determine what type of alkene is present, and if possible determine its substituents. The figure below shows the IR spectrum of a liquid measured as a capillary thin film. Take the quiz!

Quiz 7: First, determine why Table I fails for this spectrum, then using only the benzene fingers; determine the substitution pattern around the benzene ring present in the molecular structure. If possible, use the rest of the spectrum to determine the complete molecular structure of the molecule.  Take the quiz!

Quiz 6: This quiz is a two-parter. Using what you learned so far, give the substitution pattern and attempt to name each of the “molecules” seen in Figure 1. In the bottom of the figure there is a “chemical reaction”—try to name it if you can. The second and more serious part of this quiz is to finalize the identification of the molecule in the last problem (shown in Figure 2). Take the quiz!

Quiz 5: Do your best to assign all the peaks shown in the figure and table to determine the functional groups present. There is one aspect of this molecule's structure you will not be able to determine because we have not yet talked about it. Take the quiz!

Quiz 4: Do your best to assign all the peaks shown in the figure and table to determine the functional groups present. Then, put the functional groups together to come up with a proposed chemical structure. Take the quiz!

Quiz 3: Using the peak positions shown in the figure and table, do your best to assign all the peaks to determine the functional groups present. Then, put the functional groups together to come up with a proposed chemical structure. Feel free to make use of reference spectra already published in these columns. Take the quiz!

Quiz 2: Using the peak positions shown in the figure, do your best to assign all the peaks to determine the functional groups present. Then, put the functional groups together to come up with a proposed chemical structure. Take the quiz!

Quiz 1: Examine the spectrum in the figure, determine from the pattern of peaks whether the sample contains methyl groups, methylene groups, or both, and then assign as many of the peaks as you can. Take the quiz!

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