Organic Chemistry: Spectroscopy

question

infrared spectroscopy
answer

measures molecular vibrations of characteristic functional groups
question

alkanes IR C−H wavenumber
answer

2800-3000 cm⁻¹
question

alkanes IR C−C wavenumber
answer

1200 cm⁻¹
question

alkenes IR =C−H wavenumber
answer

3080-3140 cm⁻¹
question

alkenes IR C=C wavenumber
answer

1645 cm⁻¹
question

alkynes IR C≡C wavenumber
answer

2200 cm⁻¹
question

alkynes IR ≡C−H wavenumber
answer

3300 cm⁻¹
question

aromatic IR C−H wavenumber
answer

2900-3100 cm⁻¹
question

aromatic IR C−C wavenumber
answer

1475-1625 cm⁻¹
question

alcohols IR O−H wavenumber
answer

3100-3500 cm⁻¹ broad
question

ethers IR C−O wavenumber
answer

1050-1150 cm⁻¹
question

aldehydes IR (O)C−H wavenumber
answer

2700-2900 cm⁻¹
question

aldehydes IR C=O wavenumber
answer

1700-1750 cm⁻¹
question

ketones IR C=O wavenumber
answer

1700-1750 cm⁻¹
question

carboxylic acids IR C=O wavenumber
answer

1700-1750 cm⁻¹
question

carboxylic acids IR O−H wavenumber
answer

2800-3200 cm⁻¹ broad
question

amine IR N−H wavenumber
answer

3100-3500 cm⁻¹ sharp
question

IR spectroscopy guide
answer

question

UV spectroscopy
answer

involves passing ultraviolet light through a chemical sample and plotting absorbance vs. wavelength most useful for studying compounds containing double bonds and heteroatoms with lone pairs
question

¹H-NMR
answer

a form of nuclear magnetic resonance
question

chemical shifts (δ) are
answer

downfield from TMS
question

RCH₃ chemical shift
answer

0.9 ppm
question

RCH₂ chemical shift
answer

1.25 ppm
question

R₃CH chemical shift
answer

1.5 ppm
question

−CH=CH chemical shift
answer

4.6-6 ppm
question

−C≡CH chemical shift
answer

2-3 ppm
question

Ar-H chemical shift
answer

6-8.5 ppm
question

−CHX chemical shift
answer

2-4.5 ppm
question

−CHOH/−CHOR chemical shift
answer

3.4-4 ppm
question

RCHO chemical shift
answer

9-10 ppm
question

RCHCO− chemical shift
answer

2-2.5 ppm
question

−CHCOOH/−CHCOOR chemical shift
answer

2-2.6 ppm
question

−CHOH−CH₂OH chemical shift
answer

1-5.5
question

ArOH chemical shift
answer

4-12
question

−COOH chemical shift
answer

10.5-12
question

−NH₂ chemical shift
answer

1-5
question

¹H NMR guide
answer

question

when analyzing an NMR spectrum, look for
answer

1. types of protons 2. position of peaks 3. integration of peaks 4. splitting
question

types of protons
answer

correspond to the number of peaks seen in the spectrum
question

position of peaks
answer

the further left-shifted (downfield) the peak, the more deshielded the proton usually this corresponds to more electron-withdrawing groups
question

integration of peaks
answer

the larger the integration, the more protons contained under the peak
question

splitting
answer

hydrogens on adjacent carbons will split a peak into n + 1 subpeaks, where n is the number of hydrogens on the adjacent carbon

Get instant access to
all materials

Become a Member