Analytical techniques Flashcards
What is the plural terminology in spectroscopy?
Spectra
What is the key ionization method used in mass spectrometry known as?
Electron ionization (EI)
What does EI stand for in mass spectrometry?
Electron ionization
What is a mass spectrum?
A vertical bar graph representing ions with a particular m/z ratio and their relative abundance.
What are the intact molecules in a mass spectrum called?
Molecular ions
What are the ions resulting from the breakdown of a molecule in mass spectrometry called?
Fragment ions
What is the highest m/z ion typically present in a mass spectrum?
A form of the molecular ion
What is the most intense ion in a mass spectrum known as?
Base peak
What does the m/z value represent in mass spectrometry?
Mass to charge ratio
True or False: Neutral molecules can be detected in mass spectrometry.
False
What is the nitrogen rule in mass spectrometry?
Even m/z indicates even nitrogen atoms; odd m/z indicates odd nitrogen atoms.
What isotopic ratio is used to identify chlorine in mass spectrometry?
75% 35Cl and 25% 37Cl
What isotopic ratio is used to identify bromine in mass spectrometry?
50% 79Br and 50% 81Br
What is a characteristic peak size for compounds containing one chlorine?
M+2 peak is one third the size of the molecular ion.
What unusual characteristic peak do sulfur-containing compounds exhibit?
Larger than usual M+2 peak
What is the range of the IR window in spectroscopy?
4000 cm⁻¹ to 500 cm⁻¹
What do stretching vibrations in IR spectroscopy correspond to?
Increasing and decreasing bond lengths within a molecule.
What do bending vibrations in IR spectroscopy correspond to?
Increasing and decreasing angles between bonds in a molecule.
What are the N–O asymmetric and symmetric stretch wavenumbers in nitroalkanes?
- Asymmetric: 1550 cm⁻¹ * Symmetric: 1365 cm⁻¹
What does the base peak represent in an EI mass spectrum?
The most stable fragment formed in the mass spectrometer.
Fill in the blank: The tallest peak in an EI mass spectrum is called the _______.
base peak
What is the disadvantage of a harsh fragmentation technique like Electron Ionization?
May not always observe the molecular ion due to fragmentation.
What is an advantage of a harsh fragmentation technique like Electron Ionization?
Provides detailed fragmentation patterns for structure elucidation.
What should you avoid interpreting in an IR spectrum?
The fingerprint region
What is the significance of isotopic patterns in mass spectrometry?
Helps to confirm the presence of specific elements like halogens.
What is the expected M+1 peak due to?
The presence of 13C isotope in the sample.
What kind of information can IR spectroscopy provide?
Confirmation of functional groups in organic compounds.
What is the absorption of IR radiation responsible for in molecular bonds?
Causes bonds to stretch and bend.
What does the term ‘molecular ion’ refer to?
The intact ion of a molecule detected in mass spectrometry.
What is the purpose of the detector in mass spectrometry?
To detect positively charged ions.
