Study guides › C/P › Organic Chemistry
Spectroscopy & Lab Techniques
Spectra and separations are how chemists identify and purify compounds. You will read IR, 1H and 13C NMR, mass, and UV-Vis data, then choose extraction, distillation, recrystallization, or chromatography to isolate a product.
Study this chapter in PrepMed (free)
What this chapter covers
- Infrared Spectroscopy. IR tells you which functional groups are present in seconds. Learn the four or five zones and you can screen almost any answer choice.
- 1H NMR Spectroscopy. Every 1H NMR question uses four clues: the number of signals, their position, their area, and their splitting.
- 13C NMR, Mass Spectrometry & UV-Vis. These three techniques add carbon count, molecular weight, and conjugation to your evidence for a structure.
- Extraction, Distillation & Recrystallization. Separation techniques exploit differences in solubility, boiling point, or acidity. The exam asks which method fits a described mixture.
- Chromatography & Solving Unknowns. Chromatography separates by polarity, and the last skill is combining all the spectra to name an unknown structure.
Key points to know
- Broad O–H 3200–3600; acid O–H is even broader (2500–3300)
- C=O is a strong sharp peak near 1700
- Signals = sets of equivalent H; n+1 rule gives multiplicity from adjacent H
- Downfield (higher δ): near electronegative atoms, carbonyls, aromatic rings
- 13C: number of signals = number of unique carbons; C=O far downfield (160–220)
- MS: M⁺• = molecular weight; Cl gives 3:1 M/M+2, Br gives 1:1
- Acids go into aqueous base as salts, amines into aqueous acid; neutrals stay organic
- NaHCO₃ extracts carboxylic acids but not phenols; NaOH extracts both
Try a practice question
A spectrum has a very broad absorption from 2500 to 3300 cm⁻¹ and a strong sharp peak at 1710 cm⁻¹. The compound is most likely a
- primary alcohol
- ketone
- carboxylic acid
- amide
Show the answer
C. The very broad trough is the hydrogen-bonded O–H of an acid, and the C=O near 1710 fits. An alcohol has no C=O, a ketone has no broad O–H, and an amide C=O is lower with N–H bands.
Common questions
What does this chapter cover?
Spectroscopy & Lab Techniques covers Infrared Spectroscopy, 1H NMR Spectroscopy, 13C NMR, Mass Spectrometry & UV-Vis, Extraction, Distillation & Recrystallization, Chromatography & Solving Unknowns.
What should I know first?
Broad O–H 3200–3600; acid O–H is even broader (2500–3300) C=O is a strong sharp peak near 1700 Signals = sets of equivalent H; n+1 rule gives multiplicity from adjacent H
25 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.