Topic 7 Modern Analytical Techniques 1 Flashcards
What is the definition of mass-to-charge ratio?
The m/z is the ratio of the relative mass of an ion to its charge.
What is the definition of a molecular ion?
Also called a parent ion, this is the positive ion M⁺, formed when a molecule loses one electron.
What is the definition of transmittance?
The percentage of radiation which passes through the sample. Troughs that occur display the wavenumbers with high absorbance.
What is the definition of wavenumber?
The wave number is the number of waves in 1 cm of the sample.
What do the wavenumbers range from?
Infrared wavenumbers range from 400-4500 cm⁻¹.
What is a mass spectrum?
A graph that displays the mass-to-charge ratio (m/z) and their relative abundances (%) of a sample.
What is a infrared spectrum?
A graph that displays the transmittance (%) and the wavenumbers of a sample.
What is the fingerprint region on the infrared spectrum?
A complex region of the spectrum below 1500 cm⁻¹ which contains many single bond stretching and bending vibrations unique to each molecule.
What is the wavenumber that corresponds to a C=C bond?
Alkene: 1669-1645
What is the wavenumber that corresponds to a C=O bond?
Aldehyde: 1740-1720 Ketone (Alkyl): 1720-1700 Ketone (Aryl): 1700-1680 Carboxylic Acid (Alkyl): 1725-1700 Carboxylic Acid (Aryl): 1700-1680
What is the wavenumber that corresponds to a C-H bond?
Alkane: 2962-2853
Alkene: 3095-3010
Aldehyde: 2900-2820 & 2775-2700
What is the wavenumber that corresponds to a O-H bond?
Alcohols and Phenols: 3750-3200
Carboxylic Acid: 3300-2500
How can you distinguish between a O-H bond in an alcohol and in a carboxylic acid?
In a carboxylic there is a broad trough where as in an alcohol it peaks between the O-H bond and the C-H bond.
What is the absorption spectrum?
A plot showing how strongly a chemical absorbs radiation over a range of frequencies.
