IR Spectroscopy Images

Aromatic

- C-H Stretch 3100-3000

- C=C Stretch 1620-1440

- C-H Bend 900-680

Ether

Ester

- Strong C=O stretch (1765-1735 (sat.), 1730-1715 (conj.))

- strong C-O stretch

Primary amine

N-H stretch around 3300-3500

Ketone

Aldehyde

Alcohol

Carboxylic Acid

Amide

The two double peaks around 3200 and 3400 are two single bond H on a N,

Double peak between 1600-1700 almost represent a carbonyl but are too far right

Alkyne

Sharp but medium peak at ~2100

What Functional Group has a formula of C5H10O2, an intense stretch at 1715, and a very broad stretch centered at ~3100 cm-1?

AI Overview

The functional group is a

carboxylic acid. 

Here's why:

• Molecular Formula: C5H10O2 suggests a compound with two oxygen atoms and likely contains a functional group involving both carbon and oxygen.

• IR Spectrum:

  • Intense stretch at 1715 cm⁻¹: This is characteristic of a carbonyl (C=O) group. This stretch is typically strong and sharp due to the high dipole moment of the C=O bond. The range for carbonyl stretches in carboxylic acids is generally 1700-1725 cm⁻¹.

  • Very broad stretch centered at ~3100 cm⁻¹: This indicates an O-H stretch, and its broadness suggests hydrogen bonding. This is a hallmark of carboxylic acids. Carboxylic acids tend to form hydrogen-bonded dimers, leading to a very broad O-H stretch. The characteristic O-H stretch for a carboxylic acid is found in the range of 2500-3300 cm⁻¹. 

The presence of both a carbonyl group and a broad O-H stretc

What Functional Group has a formula of C5H9N and stretches at just below 3000 cm-1 and a stretch at 2250 cm-1?

1. Step 1 . Analyze the C-H stretch

2. The stretch just below

   3000cm-13000 c m to the negative 1 power

   3000𝑐𝑚−1

   indicates the presence of

   sp3s p cubed

   𝑠𝑝3

   hybridized C-H bonds.

3. Step 2 . Analyze the stretch at

   2250cm-12250 c m to the negative 1 power

   2250𝑐𝑚−1

4. The stretch at

   2250cm-12250 c m to the negative 1 power

   2250𝑐𝑚−1

   indicates the presence of a nitrile group (

   −C≡Nnegative cap C triple bar cap N

   −𝐶≡𝑁

   ).

5. Step 3 . Combine the information

6. The molecular formula

   C5H9Ncap C sub 5 cap H sub 9 cap N

   𝐶5𝐻9𝑁

   and the presence of a nitrile group suggest that the functional group is a nitrile with a four-carbon chain.

Solution 

The functional group is a nitrile.

What Functional Group has a formula of C6H10O with stretches at just below 3000 cm-1 and a strong broad stretch centered at 3350 cm-1.

1. Step 1 . Analyze the IR stretches

2. The stretch just below 3000 cm$^{-1}$ indicates C-H bonds.

3. The strong, broad stretch at 3350 cm$^{-1}$ indicates an O-H bond.

4. Step 2 . Determine the functional group

5. The presence of both C-H and O-H stretches suggests an alcohol.

6. Given the molecular formula C$_{6}

   Hcap H

   𝐻

   _{10}$O, the functional group is a cyclic alcohol.

Solution 

The functional group is a cyclic alcohol.

What Functional Group has a formula of C4H8O2 and an intense stretch at 1737 cm-1.

The functional group that has the formula C4H8O2 and an intense infrared (IR) stretch at 1737 cm-1 is most likely an ester.

Here's why:

• The molecular formula C4H8O2 suggests functional groups like carboxylic acids or esters, as they commonly contain two oxygen atoms and have one degree of unsaturation (likely a C=O bond).

• The intense stretch at 1737 cm-1 is characteristic of a carbonyl (C=O) group.

• Specifically, the C=O stretch for saturated aliphatic esters appears in the wavenumber region of 1750 to 1735 cm-1. The given value of 1737 cm-1 falls directly within this range.

• While carboxylic acids also contain a C=O stretch, their typical range for the dimer form is around 1710 cm-1, although they can be higher, particularly for the monomeric form. However, the value of 1737 cm-1 is highly characteristic of an ester. 

What Functional Group has a formula of C5H10O2, an intense stretch at 1715, and a very broad stretch centered at ~3100 cm-1?

carboxylic acid

What Functional Group has a formula of C7H12O and an intense stretch at 1724 cm-1 and stretches of moderate intensity at 2746 and 2733 cm-1

What Functional Group has a formula of C7H12O and an intense stretch at 1724 cm-1 and stretches of moderate intensity at 2746 and 2733 cm-1