Chem 124 week 1 quiz flashcards (MS, NMR, IR)

What is mass spec useful for?

Its useful to figure out the weight/mass of a molecule (and sometimes structural info based off of the weight of the fragments)

What is the instrument schematic for mass spec?

1. Gets introduced as a gas via the inlet

2. Turns into ions via ion source

3. Mass analyzer sorts out ions into sizes

4. Detector is the computer output

What does the inlet do in mass spec?

Separates mixtures into single components

What does the ion source do in mass spec?

Turns neutral molecules into ions by hitting them with high energy electrons

What does the mass analyzer do in mass spec?

Sorts out the fragments by mass to charge ratio (m/s)

What does the detector do in mass spec?

Picks up signals based off of m/s. It is then converted into a graph to be analyzed

How does a neutral molecule turn into an ion? And what ion does it become and why?

A neutral ion is hit by high energy electrons. When the electron hits the molecule, it dislodges itself and another electron (1 electron in, 2 electron out). This loss of electron creates a positive charge (cation) and a radical since there are an odd number of electrons now

What is the most important peak in mass spec?

Molecular ion

What is the molecular ion?

It is the weight of the whole molecule

Where can the molecular ion be found?

Its the peak with the largest m/z (at the very right hand side of the graph)

What is the tallest peak called? And what are some notable things about it?

Base peak. It’s the most stable and in the most abundance

What is the x axis of a mass spec graph?

mass/charge ratio aka m/z

What is the y axis of a mass spec graph?

Relative intensity aka abundance

What is another name for fragment ions?

Daughter ions

Can mass spec detect anions?

No, it can only detect cations

What are the two major isotopes in mass spec?

Chlorine and Bromine (specifically chlorine 35 and 37, and bromine 79 and 81)

What do the peaks for halogens look like?

They are M+2 and are usually two peaks that vary in size. For chlorine the peaks will have a large difference in size, but for bromine the peaks will be similar in size. Despite this, there will be two peaks regardless

Is the lower weight large or smaller in mass spec for halogens?

Larger

Which peak is the molecular ion for halogen peaks in mass spec?

The molecular ion is the larger peak out of the two and is the smaller mass

What is the peak other than the molecular peak in isotope mass spec?

Isotope peak

What is the odd nitrogen rule?

If the m/z of the molecular ion is odd, then the structure contains an odd number of nitrogens (cannot tell the exact number, only if its odd or even)

What is the smallest even number?

0

What are the steps for analyzing a mass spec?

1. find the molecular ion

2. look for isotopes

3. odd N rule

Where are the best places to split an IR for analyzing?

2500,2000,1500

What is NMR useful for?

Determining different nuclei present in a molecule

What NMR spin is the most common to see?

1/2

What NMR can is the most common to see with a ½ spin

1H and 13C NMR

What is the formula for finding ppm?

ΔRf/resonance of magnet

What are the three things you can figure out from an NMR?

1. chemical shift (ppm)

2. integration (# of hydrogens)

3. splitting pattern (neighbors)