Mass Spectra And IR Absorption Flashcards
Why are there many peaks on a mass spectrum?
Produced by fragmentation, with only cations being detected
What is the most abundant peak in the spectrum called?
Base peak
Why is there a peek just above the molecular ion peak and what is it called?
M+1
Fragments containing carbon 13
How does infrared radiation affect the molecule?
Causes them to vibrate by either stretching or bending
What is the molecular ion peak?
The highest peak
Relative molecular mass
Which bonds vibrator higher frequencies? Strong or weak
Strong bonds vibrate at higher frequencies whereas weak bonds vibrator lower frequencies
What sort of bonds vibrates at higher frequencies? Light atoms or heavier atoms
Light atoms vibrate at higher frequencies whereas heavier atoms vibrate at lower frequencies
What molecules are not affected by electromagnetic radiation? Why?
Interacts with the electrostatic dipole in the molecule therefore only molecules that change their polarity as they vibrate will absorb infrared radiation
E.g. not hydrogen but hydrogen chloride
What are the troughs called in an infrared spectrum?
Peaks
What is measured on the X axis of an infrared spectrum?
The frequency of infrared absorption is measured in wave numbers
Wavenumber (cm-1) = 1/wavelength(cm)
What is shown on the Y axis of an infrared spectrum?
Percentage transmission
The percentage of radiation that passes through a sample
What is the fingerprint region?
Unique to each compound
Located between 1400 and 800cm-1
How can you use an infrared spectrum to identify an unknown liquid?
Presence of particular bonds such as O-H can be confirmed by characteristic peaks in the identifiable parts of the spectrum
