09/10/24 Flashcards
what does CNMR detect
it detects chemically different carbons
What is broadband de-coupled 13C NMR
it detects chemically different carbon signals and only gives one peak per signal with no splitting from adjacent hydrogen fields
what is off resonance decoupled 13CNMR
it detects the splitting of protons directly attached to the carbon
it can only be used when the peaks are resolved enough
what information can we gain from a DEPT 13CNMR spectra
we can tell what type of carbons we have
what is a phase up peak representative of in a DEPT NMR
a phase up represents a CH3, or CH, it represents carbons with an odd number of hydrogens
what is a phase down peak representative of in a DEPT NMR
a phase down represents a CH2 group or groups with an even number of hydrogens
what does not appear on a DPET NMR
carbons with no hydrogens, so a carbonyl would not appear
what is the process of mass spec
a molecule is converted into ions and ion fragments through a beam of high energy electrons
what is electron impact ionization
it is the process in mass spec that zaps a molecule with a high energy beam of electrons (70eV) to dislodge one electron and create a radical cation called the molecular ion
what is the energy put into a molecule for MS
70 eV
what creates a radical cation
the dislodging of one electron in EI
what is the molecular ion
it is a positively charged ion that represents the intact molecule without fragmentation, it has the furthest signal and heaviest mass
what is the base peak in MS
it is the most abundant ion and it is the fragment that is most easily formed
what makes a ion more abundant in MS
the carbocation stability
what can the MS pick up only?
only charged ions
what types of signals does the MS pick up
it picks up the molecular ion and the daughter ions it fragments into
what is the fragment of a methyl
15 m/z
where does fragmentation first occur
at the weakest bonds that are easiest to break
what is alpha cleavage
it is the fragmentation that occurs on a molecular ion with a carbonyl or alcohol functional group
where does the alpha cleavage occur on an ether
it occurs one bond over from the C-O bond
if you have bromine in a molecule, how will it appear on an MS and why
you will have two lines in a 1:1 height ratio that are 2 mass units apart. This is due to the 50:50 abundance of Br79 and Br81
what indicates the presence of a chlorine atom in a MS
two peak heights that are 2 mass units apart with a 3:1 height ratio that represents C35 and C37
if the mass of the molecular ion is even, what is true of the formula
you either have zero nitrogens are an even number of nitrogens
if the mass of the molecular ion is odd, what is true of the formula
you are guaranteed to have at least 1 or more nitrogens (amount has to be odd)
