Infrared Spectroscopy and Mass Spectrometry

Flashcards covering the fundamental concepts, definitions, and signal interpretations of Infrared (IR) Spectroscopy and Mass Spectrometry (MS) based on the lecture notes.

Spectroscopy

The interaction between matter and light.

Photon

A light particle that travels in harmonic waves at the fastest speed possible ($2.99 \times 10^9\,m/s$ according to notes).

Wavelength

The distance between identical points on consecutive waves ($700\,nm - 50\,\mu m$ for Infrared).

Frequency

The number of waves that pass a point per unit time, which has an inverse relationship with wavelength.

Infrared Spectroscopy

A chemical analytical method that uses differing frequencies of infrared light to detect predictable types of chemical bonds.

Quantized Energy

The concept that in electromagnetic radiation and matter, the difference in energy between allowed levels is determined by the nature of the bond.

Bond Vibrations

The result of infrared radiation exciting molecules, translating into bond stretches or bends.

% Transmittance

The value plotted on the y-axis of an IR spectra.

Wavenumber ($cm^{-1}$)

The unit on the x-axis of an IR spectra; it relates to frequency and depends on bond strength and the masses of atoms sharing the bond.

Intensity (IR Signal)

A signal characteristic where some bonds absorb IR radiation efficiently (strong) and others do not (weak), depending on the strength of the dipole moment.

Shape (IR Signal)

A signal characteristic that can be very broad or narrow, often affected by factors like Hydrogen bonding.

Diagnostic Region

The region of an IR spectrum from $4000\,cm^{-1}$ to $1500\,cm^{-1}$ used to identify functional groups.

Fingerprint Region

The region of an IR spectrum from $1500\,cm^{-1}$ to $400\,cm^{-1}$.

Mass Spectrometry

The study of the interaction between matter and an energy source other than electromagnetic radiation, used to determine molecular weight and formula.

Molecular Ion ($M^{+\cdot}$)

The parent ion of a compound that is both a cation and a radical, indicating the molecular weight.

Base Peak

The most abundant ion in a mass spectrum, which may not always be the molecular ion.

Nitrogen Rule

A rule stating that an odd nominal molecular mass ($M$) indicates an odd number of nitrogen atoms are present.

$(M+1)^{+\cdot}$ Peak

A peak occurring because of the presence of the $^{13}C$ isotope, which comprises approximately $1.1\%$ of all carbon.

$(M+2)^{+\cdot}$ Peak

A peak occurring in compounds containing isotopes like Chlorine ($Cl^{35}$ and $Cl^{37}$ in a $3:1$ ratio) or Bromine ($Br^{79}$ and $Br^{81}$ in a $1:1$ ratio).

Dehydration (MS Fragmentation)

A fragmentation pattern specifically for alcohols resulting in a mass loss of $M-18$ (loss of water).

McLafferty Rearrangement

A fragmentation pattern undergone by ketones or aldehydes that results in the loss of a neutral alkene.

Hydrogen Deficiency Index (HDI)

A measure of the number of degrees of unsaturation calculated as $\frac{1}{2}(2C + 2 + N - H - X)$.