Chem unit 9.2 Analytical Chem

what does the Mass Spectrometry do

of organic compounds can cause the fragmentation of molecules to show molar mass

uses no electromagnetic radiation

on x-axis, it is mass/charge ratio essentially just mass

the last peak comes from the parent ion, or molecular ion, the ones before are the fragments of the molecule.

due to the isotopes of carbon atoms (carbon 13), there may be another small peak after

by breaking the molecule down by each functional group we can predict some of the peaks with their distinct molar mass — all written as ions

how does IR spec work

moles have covalent bonds, some bonds absorb certain parts of the infrared spectrum causing bond is stretching; it will only happen if the bond stretching causes a polarity change or change in the dipole moment

What are obvious observations on IR Spec

O-H large and wide peak

C=O large thin peak

TABLE 20

we only look at left side of graph

What does HNMR use to work and what does it show

uses radio waves to show the different chemical environments for hydrogen, with a ratio of the hydrogen to the number of environments.

It uses strong magnets to cause nuclei to align in different spin states resulting in radio wave emission

the number of different groups of peaks, shows how many environments there are

TABLE 21

How to name HNMR spectrum peaks

one peak = singlet

• no hydrogen atoms next to it

two peaks = doublet

• one hydrogen next to it

one peak two small ones = triplet

• two hydrogen atoms next to it

two peaks two small ones = quartet

• having a quartet means that there are 3 hydrogens next to the hydrogen, such as CH2CH3, the CH2 will show up as a quartet and CH3 will show up as triplet

anything more = multiplet

to the left is an environment with OH whereas methyl is right

integration trace

how many hydrogens are in one environment

exception for HNMR peaks

alcohol does not display splitting; anything next to it will be singlet;

CH3OH the CH3 will show up as a singlet

but OH is still found on graph, nect to three other hydrogens multiplet

What does the molecular ion in mass spec show

gives the relative molecular mass of the molecule

what does splitting pattern mean on HNMR

the singlet, etc

what does ratio of areas mean

integration trace

what happens when molecule absobrbs IR

bond angle chnages and teh bond strechtes causing a polarity change