Chapter 14 Flashcards
Define Mass Spectrometry
An analytic method used to study interaction between matter and an energy source. Used to find MW and formula for a compound
How does a mass spectrometer work?
Compound is vaporized and converted to ions, then separated and detected by passing through magnetic field. Most common is hitting it with high-energy electrons
EI stands for?
Electron Impact Ionization - a ionization technique when a compound gets hit with high-energy electrons (generates radical & cation)
What is a radical symbolized by and what is it called (2 names)
(M)^(+•) : molecular or parent ion
What is generated in fragmentation?
A molecular ion that breaks apart and creates a fragment with an unpaired electron and a fragment with the charge
What kind of plot can be made with mass spec?
A mass spectrum, shows relative abundance of every cation detected
Can a base peak always be the molecular ion peak?
No, for larger compounds it’s common for other fragments to have the tallest peak
How do isotopes differ?
In their number of neutrons which changes its atomic mass
Compare the (M)^(+•) and base peak
(M)^(+•) peak is the first radical cation generated in fragmentation (100%) and the compounds MW. The base peak is the most abundant cation that passes through the mass spectrometer
What does an odd or even molecular weight tell us?
Odd tells us odd number of nitrogen. Even means even or absence of N
How is the (M+1)^(+•) peak determined if the molecular ion peak is NOT the base peak?
(Rel. abun. of M+1)/(Rel. abun. of M+) then *100 then divide by abundance in nature
How do you analyze the (M+2) peaks?
This indicates that there are 2 major isotopes of the element chlorine and bromine rather than 1 isotope. Bromine isotopes 79 & 81 are almost equally abundant in nature while chlorine 35 & 37 are not
Define saturation
There are no pi bonds meaning there are a maximum number of hydrogens relative to carbons
Define unsaturated
A compound with a pi bonds (or ring structure) since it as fewer hydrogens relative to carbons
What does one degree of unsaturation mean?
Two hydrogen atoms are missing
How many combinations are there in 2 degrees of saturation ?
Two pi bonds, one triple bond, one pi bond and a ring, or two rings
What is HDI
- measure of degrees of unsaturation
= (1/2) (2C +2 +N -H -X)
