Organic Chemistry 2 Exam 1

0-40 ppm Chemical shift

Sp3 C-C

40-100 ppm chemical shift

Sp3 C-X (X = electronegative atom)

80-100 ppm chemical shift

CC triple bond

100-150 ppm chemical shift

C=C, aromatic ring

150-200 ppm chemical shift

Acid halide

>200 ppm chemical shift

Chemical shifts (REVIEW)

0.9 ppm chemical shift

Type of Proton

Methyl

1.3 ppm chemical shift

Type of Proton

Methylene

1.4 ppm chemical shift

Type of Proton

Methine

2.1 ppm chemical shift

Type of Proton

Methyl Ketone

2.5 ppm chemical shift

Type of Proton

Acetylenic

3-4 ppm chemical shift

Type of Proton

(X=halogen, O)

5-6 ppm chemical shift

Type of Proton

Vinyl

1.7 ppm chemical shift

Type of Proton

Allylic Hydrogen

7.2 ppm chemical shift

Type of Proton

Aromatic

2.3 ppm chemical shift

Type of Proton

Benzylic

9-10 ppm chemical shift

Type of Proton

Aldehyde

10-12 ppm chemical shift

Type of Proton

Acid

Variable ~2-5 ppm chemical shift

Type of Proton

Alcohol

Variable, ~4-7 ppm chemical shift

Type of Proton

Phenol

Variable, ~1.5-4

Amine

Chemical Shift of methyl H

4.3 ppm

Chemical Shift of methyl H

3.4 ppm

Chemical Shift of methyl H

3.0 ppm

Chemical Shift of methyl H

2.7 ppm

Chemical Shift of methyl H

2.2 ppm

Chemical Shift of methyl H

0.9 ppm

Chemical Shift of methyl H

0.0 ppm

Wave number of H3-CH3 Bond

995 cm-1

Wave number of H2C=CH2 Bond

1650 cm-1

Wavenumber of HC triple bond CH

2181 cm-1

Wavenumber of C-F

1049 cm-1

Wavenumber of C-Cl

732 cm-1

Wavenumber of C-Br

611 cm-1

Wavenumber of carbonyl

1715 cm-1

Wavenumber of C(sp3)—H

2900cm-1

Wavenumber of C(sp2)—H

3100 cm-1

Wavenumber of C=C

1660cm-1

Wavenumber of Terminal Alkynes (2 kinds)

C triple bond C 2200cm-1

C(sp)-H 3100cm-1

Wavenumber of Internal Alkynes

No Csp-H bond stretch around 3100cm-1 and C TRIPLE BOND C stretch (2100cm-1) —» OFTEN MISSING IF MOLECULE ISN’T POLAR

Wavenumber of Alcohol

O-H stretch 3400cm-1 (very intense bc of polarity)

(Only fingerprint areas of IR to pay attention to is the C-O bond)

Characteristic broad OH band is result of H-bonding; “free OH” is not H-bonded to other molecules (Rounded tips = broad bands; sharp ended possibly indicates “free OH” but this is rare)

Wavenumber of Ethers

C-O stretching band around 1100cm-1 —» will look jagged like ^^^^^ or flat like ———

Wavenumber of Ketones

C=O stretch around 1715 cm-1 (carbonyl)

Wavenumber of Aldehydes

C=O stretch around 1735cm-1

• Two distinct aldehyde C-H bands at 2840cm-1 and 2710cm-1

Wavenumber of Carboxylic Acid

Broad O-H band extends from 3600-2400cm-1 (broad range due to high polarity)

C=O stretch around 1715cm-1

Wavenumber of Esters

C=O stretch around 1740cm-1, two C-O stretching bands around 1100 cm-1 in fingerprint regions (C-O bond)

Wavenumber of Amides

C=O stretch below 1700cm-1; N-H if there’s H atom in N, visible at 3300cm-1

Wavenumber of Aromatic

Always looks more complex than other functional groups; overtone region contains several (usually 4 → index of H deficiency) low intensity peaks between 2000-1600cm-1

=C–H stretch is observed at 3100-3000 cm^-1

what does wavenumber tell you about bonds?

Indicates the energy of the bond vibrations and the strength of bond and atomic mass. Higher wavenumbers = stronger bonds and lighter atoms, lower wavenumbers = weaker bonds and heavier atoms

Single bonds: below 1500cm-1

Double bonds: ~1700cm-1

Triple bonds: ~2200cm-1

What does chemical shift tell you about bonds and molecules"?

Local electron environment, the magnetic shielding, and nuclei structure

Identifies functional groups; e withdrawing groups deshield nuclei moving peaks downfield/higher ppm and vice versa with e donating groups (shielding)

Common wavenumbers

4000-2500 cm-1: O−H, N−H, 𝐶−𝐻 stretching (light atoms)

2500-2000 cm-1: C≡C, 𝐶≡𝑁 stretching (triple bonds).

2000-1500 cm-1: C=O, C=C, C=N stretching (double bonds).

Below 1500 cm-1: Fingerprint region (single bonds, bending motions)