Mass Spectroscopy

Question 1

Determines molecular weight and molecular formula

Answer 1

Mass spectrometry (ms)

Question 2

 Basic principle behind mass spectroscopy

Answer 2

An unknown neutral sample is vaporized with heat under vacuum
Is bombarded with a stream of high energy electrons
It is an ion is under the collision impact
-cation radicals, then fragmented into smaller positive or neutral pieces
-The positive fragments are accelerated towards two negative plates
-The positive fragments are channeled through a curved analyzer in a magnetic field, then sorted according to their masses

Question 3

Mass spec is sorted by ________ fragments

Answer 3

Positive

Question 4

A mass spectrum is a plot of ______ values vs. The intensity or relative abundance in %

Answer 4

M/Z

Question 5

Tallest peak in a spectrum, it corresponds to the most abundant fragment

Answer 5

Base peak

Question 6

 Peak corresponding to the unfragmented cat ion radical, M+

Answer 6

Parent Peak

Question 7

_____ Is called the molecular ion or parent ion so, the parent P is the peak corresponding to the parent Ion

Answer 7

M+•

Question 8

Note: The parent peak can also be the ____ peak

Answer 8

Base

Question 9

From the m/z of the molecular or parent ion, one can get the _________ of a compound.

Answer 9

Molecular weight

Question 10

Mass spectrometry can also be used to identify an unknown substance by….

Answer 10

Comparing its mass spectrum to known mass spectra

Question 11

Small peak due to the presence of small amount of isotopic and or deuterium

Answer 11

The M+1 peak

Question 12

This peak is due to the presence of CL or BR. Cl and Br each had two major isotopes

Answer 12

the M+2 peak

Question 13

Cl occurs in a ___:___ ratio

Answer 13

3:1

Question 14

Br occurs naturally as Br-79 and Br-81 in a ___:___ ratio

Answer 14

1:1

Question 15

What is rule number one for determining molecular formulas?

Answer 15

How do you spell ribbons and organic molecules that contain only C,H, and O always have even molecular weights

Question 16

What is rule number two for determining molecular formulas?

Answer 16

The nitrogen rule: compound that contain an odd number of N atoms have odd molecular weights. Compounds that contain an even number of atoms have even molecular weights.