09/10/24

Question 1

what does CNMR detect

Answer 1

it detects chemically different carbons

Question 2

What is broadband de-coupled 13C NMR

Answer 2

it detects chemically different carbon signals and only gives one peak per signal with no splitting from adjacent hydrogen fields

Question 3

what is off resonance decoupled 13CNMR

Answer 3

it detects the splitting of protons directly attached to the carbon

it can only be used when the peaks are resolved enough

Question 4

what information can we gain from a DEPT 13CNMR spectra

Answer 4

we can tell what type of carbons we have

Question 5

what is a phase up peak representative of in a DEPT NMR

Answer 5

a phase up represents a CH3, or CH, it represents carbons with an odd number of hydrogens

Question 6

what is a phase down peak representative of in a DEPT NMR

Answer 6

a phase down represents a CH2 group or groups with an even number of hydrogens

Question 7

what does not appear on a DPET NMR

Answer 7

carbons with no hydrogens, so a carbonyl would not appear

Question 8

what is the process of mass spec

Answer 8

a molecule is converted into ions and ion fragments through a beam of high energy electrons

Question 9

what is electron impact ionization

Answer 9

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

Question 10

what is the energy put into a molecule for MS

Answer 10

70 eV

Question 11

what creates a radical cation

Answer 11

the dislodging of one electron in EI

Question 12

what is the molecular ion

Answer 12

it is a positively charged ion that represents the intact molecule without fragmentation, it has the furthest signal and heaviest mass

Question 13

what is the base peak in MS

Answer 13

it is the most abundant ion and it is the fragment that is most easily formed

Question 14

what makes a ion more abundant in MS

Answer 14

the carbocation stability

Question 15

what can the MS pick up only?

Answer 15

only charged ions

Question 16

what types of signals does the MS pick up

Answer 16

it picks up the molecular ion and the daughter ions it fragments into

Question 17

what is the fragment of a methyl

Answer 17

15 m/z

Question 18

where does fragmentation first occur

Answer 18

at the weakest bonds that are easiest to break

Question 19

what is alpha cleavage

Answer 19

it is the fragmentation that occurs on a molecular ion with a carbonyl or alcohol functional group

Question 20

where does the alpha cleavage occur on an ether

Answer 20

it occurs one bond over from the C-O bond

Question 21

if you have bromine in a molecule, how will it appear on an MS and why

Answer 21

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

Question 22

what indicates the presence of a chlorine atom in a MS

Answer 22

two peak heights that are 2 mass units apart with a 3:1 height ratio that represents C35 and C37

Question 23

if the mass of the molecular ion is even, what is true of the formula

Answer 23

you either have zero nitrogens are an even number of nitrogens

Question 24

if the mass of the molecular ion is odd, what is true of the formula

Answer 24

you are guaranteed to have at least 1 or more nitrogens (amount has to be odd)