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What Is NMR Spectroscopy? - 19B
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A Level Analytical Techniques (Edexcel)
In this course, Dr Noha Ziedan (University of Chester) talks to us about key analytical techniques used in your A-level specification. We begin by (i) looking at NMR spectroscopy and learning its fundamental principles that allows it to work (Topic 19B); such as (ii) number of signals (Topic 19B); (iii) chemical shift (Topic 19B); (iv) integration values (Topic 19B); and (v) spin-spin coupling (Topic 19B); before looking at two sample compounds: (vi) 1,1-dibromopropane (Topic 19B); and (vii) ethyl acetate (Topic 19B); and then move onto (viii) infrared spectroscopy as a method of analysis (Topic 7B); and (ix) how we can use it to identify functional groups in three different organic compounds (Topic 7B); and (x) understand using the same principles how greenhouse gases heat the planet; before (xi) moving onto mass spectrometry (Topic 7A); and finally (xii) understand what a mass spectrum can tell us about a compound (Topic 7A).
What Is NMR Spectroscopy? - 19B
In this lecture, we begin our discussion of analytical techniques by focusing on nuclear magnetic resonance (NMR) spectroscopy (Topic 19B). We learn about the fundamental principles that NMR spectroscopy relies on, such as the interaction between spinning nuclei and applied magnetic fields, causing nuclei to align with or against the magnetic field. When irradiated with radiofrequency radiation, nuclei absorb energy, flipping their alignment. This energy difference is measured as chemical shifts in parts per million on the x-axis of an NMR spectrum, revealing structural information about the molecules. Proton NMR and Carbon-13 NMR are explored as essential nuclei for analysis.
Hi. My name is Doctor. No. I'm your lecturer,
00:00:06at University of Chester,
00:00:09and I mainly teach organic chemistry and medicinal chemistry.
00:00:11Today I'm going to talk to you about the different analytical
00:00:15techniques you need to use for identification of organic
00:00:19compounds as per your level exam board. So, the first,
00:00:22analytical technique we are going to talk about is nuclear
00:00:28magnetic core resonance. So have you ever wondered how we
00:00:31as organic chemist, tend to know the structure of our
00:00:35products because we tend to do reactions on a daily basis.
00:00:40And sometimes we are,
00:00:44we cannot actually see our project with our eyes, but we
00:00:45need to find the of these molecules.
00:00:49So we we use different analytical techniques to
00:00:52identify the structure of these molecules. The one we use on a
00:00:56daily basis is basically the NMR or nuclear magnetic resonance.
00:01:00Most of not all of the analytical techniques will
00:01:06depend on the interaction between the atoms and or
00:01:09between the molecules and the electromagnetic radiation.
00:01:13So electromagnetic radiation,
00:01:17have photons with some energy. They differ in their energy
00:01:20depending on which region in the electromagnetic radiation,
00:01:24when a molecule or an atom absorb the light, or absorb
00:01:27photons from a certain region of electromagnetic radiation
00:01:32with a certain energy that tends to cause some changes in
00:01:35that molecule or in that atom.
00:01:39The amount of energy that has been absorbed can be measured
00:01:41and will give us a signal that will give us some information
00:01:45about the structure.
00:01:49So let's start by talking about the NMR. So let's
00:01:50hear this statement and try to analyze it step by step.
00:01:54So nuclear magnetic resonance spectroscopy
00:01:57is an instrumental technique based on monitoring how we're
00:02:01spinning nuclei with magnetic dipole interact with applied
00:02:04magnetic field and absorb radiation.
00:02:09Probably this sentence doesn't make a lot of sense to you,
00:02:12but let's analyze it and explain it. So the first thing
00:02:15we said that spinning nuclei,
00:02:19what are the nuclei? What are the spinning nuclei? So nuclei,
00:02:22that have an odd number of, near fumes or
00:02:27basically the total of electrons, of protons and
00:02:32nutrients will have a spin.
00:02:36They will tend to spend like a magnet.
00:02:38But the ones that have an even number, a total even number,
00:02:40they will not have the spend number.
00:02:44They will not have a spend like a magnet. So how would we know
00:02:47whether they are hot or even?
00:02:52Remember that the mass number of, an atom
00:02:54it's basically the total number of
00:02:59nutrients and protons inside the nucleus.
00:03:02So the atoms that have an odd, mass number
00:03:05are the one that will have spin. The one that don't will
00:03:11not have a spin.
00:03:15So these are the one that we are going to study.
00:03:16The one with an odd number There are only two nuclei or
00:03:19two types of, nuclei that we are going to study for
00:03:23nucleolytic resonance, which are the proton NMR and the
00:03:28Carbon thirteen NMR.
00:03:32So proton is the high So the hydrogen
00:03:34hydrogen one, we know that the isotope of hydrogen,
00:03:37this is the most abundant isotope of hydrogen in the
00:03:40hydrogen one. It only has one proton, This is why we call
00:03:43hydrogen one NMR as proton NMR. And the second one is the Carbon thirteen.
00:03:47So know the most abundant isotope of carbon in the
00:03:53carbon-twelve, but it has an even number of,
00:03:55mass number or an even number of nutrients and protons,
00:03:59which is twelve, so it doesn't have a span.
00:04:03Carbon thirteen has an abundance of around one
00:04:05percent, so it will have a span and it can give us a signal
00:04:08in the, in a more. So Carbon thirteen and Proton or hydrogen
00:04:13one are the one we need to study and blow about here.
00:04:17So this is the first thing. This is the spending nuclei. So
00:04:21how can we make use of this? So this is spending nuclei when
00:04:25without an applied magnetic field,
00:04:29they were just spin in all directions.
00:04:31So,
00:04:33basically imagine that one is creating a small magnetic field
00:04:33in one direction,
00:04:37the other one is creating think I'm medically on the other direction,
00:04:38so they would cancel each other out because they this is random
00:04:41spending in all directions for all of the nuclei
00:04:44So once you bought an external magnetic field, these
00:04:48nuclei will start to arrange themselves into two different
00:04:52positions. The first one,
00:04:57they will start to spin and align themselves with the
00:04:59external magnetic field. So they are basically within the same,
00:05:02the same direction as external magnetic field. There are also another
00:05:07state where they will be aligned opposite to the
00:05:12external magnetic field.
00:05:16There's a difference in the energy between these two states
00:05:18normally, most of the,
00:05:22nuclei will be arranged with the external magnetic field
00:05:24because it's lower energy
00:05:27very tiny ones will be arranged to,
00:05:30opposite to the external magnetic field. But if we
00:05:33irradiate these nuclei, which are in these, magnetic fields to,
00:05:37electromagnetic radiation with the radio frequency range,
00:05:45then the energy of this radio frequency
00:05:49are just enough to cause the flipping of one state to
00:05:52another. So basically, this nuclei, if they absorb enough
00:05:56energy that covers the difference in the energy
00:06:01between the two, states.
00:06:04So then the difference in the energy between the two states
00:06:07they can flip from being arranged with the external
00:06:11magnetic field to be arranged against the external magnetic
00:06:14field. And this difference in the energy, this amount of,
00:06:18of radio frequency that has been absorbed and led to this
00:06:23let's do this flipping,
00:06:28can be actually measured and will give us a signal that will
00:06:30give us some information about the structure of our NMR. So the
00:06:34NMR,
00:06:39basically, what we get at the end is that we're gonna get
00:06:41a spectrum on the x axis is called the chemical shift. And
00:06:45we, the chemical shift, we give it the,
00:06:50sample delta and we measure it in part per million,
00:06:52and will give us some signals that we're gonna see these signals.
00:06:55Each signal will give us some information about our structure
00:06:59and the y axis is simply the intensity of the signals. So
00:07:03this is the main theory about how the NMR work and
00:07:07how we can find the structure of molecules or apply the theory,
00:07:11of the NMR to find the structure.
00:07:16
Cite this Lecture
APA style
Ziedan, N. (2023, October 24). A Level Analytical Techniques (Edexcel) - What Is NMR Spectroscopy? - 19B [Video]. MASSOLIT. https://massolit.io/courses/a-level-analytical-techniques-edexcel/effect-of-greenhouse-gases-on-the-climate
MLA style
Ziedan, N. "A Level Analytical Techniques (Edexcel) – What Is NMR Spectroscopy? - 19B." MASSOLIT, uploaded by MASSOLIT, 24 Oct 2023, https://massolit.io/courses/a-level-analytical-techniques-edexcel/effect-of-greenhouse-gases-on-the-climate