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IR spectroscopy explaination :-

Explanation:

Infrared (IR) spectroscopy measures the vibrational modes of covalent bonds in a molecule. When a molecule absorbs infrared radiation, it undergoes a change in its vibrational energy. The absorbed energy corresponds to the frequency of the infrared radiation, which is related to the vibrational frequency of the covalent bonds in the molecule.

The units of IR spectroscopy are wavenumbers (cm^-1), which represent the number of waves per centimeter. The wavenumber is proportional to the frequency of the infrared radiation and is inversely proportional to the wavelength.

The abbreviations used to describe the shape and intensity of IR absorbance peaks are as follows:

m: medium intensity
w: weak intensity
s: strong intensity
b: broad shape (usually due to hydrogen bonding or overlapping peaks)
n: narrow shape (usually due to a pure functional group)
sh: shoulder (a small peak that appears next to a larger peak and indicates the presence of a related functional group)

By analyzing the positions and intensities of IR absorbance peaks, we can identify the functional groups present in a molecule and determine its structure. For example, the presence of an O-H stretch in the IR spectrum indicates the presence of an alcohol group, while the presence of a C=O stretch indicates the presence of a carbonyl group (such as in a ketone or aldehyde).

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Difference between the peaks :-

Explanation:

In IR spectroscopy, the N-H and O-H peaks are characteristic of functional groups that contain nitrogen or oxygen atoms, respectively, attached to hydrogen atoms. By analyzing the positions and shapes of these peaks, we can distinguish between different types of compounds, including alcohols, primary amines, and secondary amines.

Alcohols typically have a broad, strong peak in the range of 3200-3600 cm^-1 due to the O-H stretch. The exact position of this peak can vary depending on the type of alcohol, as well as the presence of hydrogen bonding. For example, ethanol has an O-H stretch at around 3300 cm^-1, while phenol (an aromatic alcohol) has a broad O-H stretch at around 3600 cm^-1 due to strong hydrogen bonding.

Primary amines typically have a sharp, strong peak in the range of 3300-3500 cm^-1 due to the N-H stretch. This peak is usually broader and slightly lower in energy than the O-H stretch of alcohols. For example, ethylamine has a N-H stretch at around 3300 cm^-1.

Secondary amines also have a N-H stretch, but the peak is typically weaker and occurs at a lower frequency than that of primary amines. Secondary amines also have a C-N stretch peak in the range of 1350-1600 cm^-1. For example, dimethylamine has a weak N-H stretch at around 3300 cm^-1 and a C-N stretch at around 1500 cm^-1.

Here is a summary of the characteristic peaks for alcohols, primary amines, and secondary amines in IR spectroscopy:

Alcohols: broad, strong O-H stretch at 3200-3600 cm^-1
Primary amines: sharp, strong N-H stretch at 3300-3500 cm^-1
Secondary amines: weak N-H stretch at 3300-3500 cm^-1 and C-N stretch at 1350-1600 cm^-1

It's important to note that the exact positions and shapes of these peaks can vary depending on the specific molecule and the conditions of the IR experiment (such as the solvent used). Therefore, it's important to use a combination of different spectroscopic techniques and chemical tests to confirm the identity of a compoound.

1. What does IR spectroscopy measure in a molecule? What are the units? Define each of the abbreviations used to describe absorbance peaks (m, w, s, b, n, sh). 2. How can you tell the difference between an alcohol, a primary amine, and a secondary amine in the N-H or O-H peak? Show examples.

Public Answer

1. What does IR spectroscopy measure in a molecule? What are the units? Define each of the abbreviations used to describe absorbance peaks (m, w, s, b, n, sh).

2. How can you tell the difference between an alcohol, a primary amine, and a secondary amine in the N-H or O-H peak? Show examples.