spectroscopy

What does IR spectroscopy identify?

Functional groups in a molecule based on bond vibrations caused by infrared radiation.

What type of bonds are IR inactive?

Symmetrical bonds with no net dipole (e.g., O₂, N₂, C≡C, C=C).

What does a large, broad IR peak at 3200–3500 cm⁻¹ indicate?

Alcohol (-OH).

What does a sharp IR peak at 3200–3500 cm⁻¹ indicate?

Amine (-NH); 1 peak for secondary, 2 peaks for primary.

What functional group gives a jagged broad IR peak from 2500–3500 cm⁻¹?

Carboxylic acid (-COOH).

What IR region indicates a nitrile group (C≡N)?

Medium peak at 2200–2250 cm⁻¹.

What IR region corresponds to carbonyl (C=O)?

Sharp, large peak at 1700–1750 cm⁻¹.

What is the purpose of ¹H NMR?

To identify hydrogen environments in a compound.

What determines if protons are chemically equivalent in ¹H NMR?

Same chemical environment.

What does the n+1 rule in ¹H NMR predict?

Number of signal peaks = number of neighboring protons + 1.

What is downfield in NMR?

Deshielded protons (closer to electronegative atoms), appear left on the spectrum.

What is upfield in NMR?

Shielded protons (more electron density), appear right on the spectrum.

What does integration in NMR indicate?

Relative number of protons for each signal.

What does ¹³C NMR measure?

Distinct signals for chemically non-equivalent carbon atoms.

What is the most important use of ¹³C NMR for the DAT?

Identifying carbonyl-containing functional groups.

Formula to calculate degrees of unsaturation?

(2C + 2 + N - H - X) ÷ 2

What does each degree of unsaturation represent?

One ring or one π bond.

What does mass spectrometry determine?

Mass and structure of a molecule.

What is the molecular ion peak in mass spectrometry?

Represents the compound's molecular mass.

What does UV-Vis spectroscopy analyze?

Conjugated π bonds; more conjugation = longer λmax.

What is extraction used for in lab techniques?

Separating compounds based on solubility in aqueous vs organic layers.

In extraction, where do acidic or basic compounds go when ionized?

Aqueous layer (charged forms).

What does TLC separate compounds by?

Polarity and intermolecular forces.

How do polar vs non-polar compounds behave in TLC?

Non-polar travel further (higher Rf); polar travel less (lower Rf).

Column chromatography separates compounds by?

Polarity; non-polar elutes first, polar elutes last.

What does gas-liquid chromatography separate by?

Boiling point and solubility in liquid phase; lower BP = faster elution.

Simple vs. fractional distillation?

Simple: >50°C BP difference; Fractional: <25°C BP difference.

What is recrystallization used for?

Purifying solids based on solubility changes with temperature.