Spectroscopy Topic 1 Flashcards
What is spectroscopy?
It is usually definrd as the interaction between matter and electromagnetic radiation.
How Infra-red spectroscopy works?
Electromagnetic frequency in the IR region corresponds to the frequencies at which covalent bonds vibrate (stretching or bending). Bonds such as O-H, C-H, C=O, and C=C give characteristic absorption bands in the IR spectrum.
What is the main use of Infra-red spectroscopy?
To identify functional groups.
What is the most important part in IR spectrum?
Approximately 400 to 4000 cm-1
What is the most important part in UV/Vis spectrum?
For UV it is approximately 190 and 400 nm and for visible is between 400 and 700 nm.
What UV/Vis spectroscopy is used for?
It reveal the presence of a conjugated π system.
With what UV or visible light spectroscopy is asssociated with?
With the transition of electrons between orbitals.
How NMR spectroscopy works?
It works by detecting transitions between the orientation of the nuclear magnetic dipole in an external magnetic field. The energy gap between these states is small, and corresponds to the radiofrequency region of the EM spectrum.
What is chemical shift (σ)?
It is a horizontal scale in NMR and is measured in ppm. It is relative frequency scale, with the absorption frequency of tetramethylsilane as the referance compound.
What signals in chemical shift indicates?
It indicates the chemical environment of the nuclei and provides structural information.
What chemical shift range 13CNMR covers?
0-220 ppm.
Why 13CNMR spectrum is called proton decaupled spectrum?
13C spectra are usually presented in a way that gives a single signal for each non-equivalent carbon atom in a molecule. This requires removal of coupling from 1H nuclei in the molecule.
What chemical shift range 1HNMR covers?
0-12 ppm.
What features are presented in a 1H NMR spectrum?
Chemical chift (proton environment)
Signal intensity (relative number of protons in a given signal)
spin-spin coupling (number of near-by protons)
What mass spectroscopy measures and why?
It measures mass-to-charge ratio of gas-phase ion. This can provide structural information through measurement of molecular mass and fragment analysis.
