If the extinction coefficient can be calculated from a single absorbance measurement at a known concentration of a compound, a) why is a calibration curve necessary, even if the measured absorbance is below 1? b) Why should absorbance be less than 2? Please explain in terms of light transmittance.

Counterfeit drugs are a common problem in developing regions of the world. Oftentimes, counterfeit pills are made with compounds such as lactose. A lab technician has obtained the IR spectrum shown above for a sample reported to be citalopram, an antidepressant drug. Does the IR spectrum belong to citalopram or lactose? Explain your answer by describing what feature of the IR spectrum confirms your choice and describe what feature is missing from the IR spectrum for the other compound. A. citalopram B. lactose

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Draw structures for the three isomers 1-butyne, 1,3-butadiene, and 2-butyne. Explain how you would distinguish these compounds using IR spectroscopy. Give specific examples of peaks that would illustrate the differences.