<< Chapter < Page Chapter >> Page >

We can also use integration to find the relative amounts of substances present. For example, if we have a mixture of iodomethane and chloromethane dissolved in solution, the ratio of the two peak areas will give the relative amounts of these two compounds. This is useful for determining purity and product yield. We can introduce a known amount of one sample and use its concentration to determine the concentration of another species in solution. The one caution here is that the relative peak areas need to be normalized for the number of protons that produce the signal. In the example of iodomethane and chloromethane, this is easy since they both have methyl groups and the signals are both due to three protons. However, if we were to determine the concentration of dichloromethane versus chloromethane, we would need to take into account that one molecule has three H atoms whereas the other only has two.

Examples:

Butane

The two methyl groups are equivalent to each other, as are the two methylene groups. We would expect to see two signals in a 6:4 or 3:2 ratio.

Pentane

The two methyl groups are equivalent to each other, as are two of the two methylene groups. The middle methylene group is unique. In principle, we would expect to see three signals in a 6:4:2 or 3:2:1 ratio.

Ethyl acetate

Ethyl acetate has three types of H atoms. There are two methyl groups and one methylene group. We would expect to see three signals in a 3:3:2 area ratio.

Coupling

Coupling is another very important aspect of NMR spectroscopy that gives a great deal of information about structure. Coupling results in a signal being split into more signals due to neighboring atoms which also have a nuclear spin. This arises frequently between protons on adjacent carbon atoms. One important aspect of this phenomenon is that equivalent nuclei do not couple to each other.

The reason coupling occurs can be described as follows. For example, let us consider the case of a molecule containing two carbon atoms, each with a single proton and other atoms which do not have a nuclear spin coupling to the protons. One such molecule is 1,1-dibromo-2,2-dichloroethane.

The protons in this molecule are not equivalent, so we would expect to see two signals. Additionally, the proton attached to the CCl 2 size 12{ ital "CCl" rSub { size 8{2} } } {} group will have two different spin states, +1/2 and -1/2. This means that the proton on the CBr 2 size 12{ ital "CBr" rSub { size 8{2} } } {} group will see two slightly different magnetic fields depending upon whether the proton on the CCl 2 size 12{ ital "CCl" rSub { size 8{2} } } {} group is in the +1/2 or -1/2 spin state. Since these spin states are not equivalent in the presence of a large external magnetic field, we actually observe two signals for the H atom attached to the CBr 2 size 12{ ital "CBr" rSub { size 8{2} } } {} group. This is also true for the hydrogen atom attached to the CCl 2 size 12{ ital "CCl" rSub { size 8{2} } } {} group. In these situations, we say that the proton on the CCl 2 size 12{ ital "CCl" rSub { size 8{2} } } {} is coupled to the proton on the CBr 2 size 12{ ital "CBr" rSub { size 8{2} } } {} group. When a peak is split into two equal components by coupling, it is called a doublet. We would expect the proton NMR spectrum of 1,1-dibromo-2,2-dichloroethane to look something like this:

Questions & Answers

I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
How can I make nanorobot?
Lily
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Chem 215 spring08. OpenStax CNX. Mar 21, 2008 Download for free at http://cnx.org/content/col10496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chem 215 spring08' conversation and receive update notifications?

Ask