NMR Principle and Spin Properties
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Questions and Answers

Wanem prinsipol blong NMR?

NMR i stap lukluk long niuklies blong wan atom we i stap insaed long wan fild blong magnetik. Hem i stap lukluk long niuklies ia taem we i stap kasem radiasion blong electromagnetic. Radiasion ia i stap kasem niuklies long wan spesifik frekwens we i mak long radiasion ia.

NMR i stap yusum ______ radiasion.

Radio Frequens (RF)

Olgeta niuklies i stap wetem SPIN.

False

Wanem element we i gat SPIN?

<p>13C</p> Signup and view all the answers

Ol niuklies we i gat SPIN i stap ______ long NMR

<p>detectable</p> Signup and view all the answers

Ol atom we i gat wan nomba blong proton we i EVEN i stap wetem SPIN.

<p>False</p> Signup and view all the answers

Wanem saens blong SPIN?

<p>Saens blong SPIN i stap mak long I, we i stap kol SPIN kwantam nomba. Saens ia i save stap long ol nomba ia: 0, 1/2, 1, 3/2, 2, 5/2, ....</p> Signup and view all the answers

Ol niuklies we i gat wan nomba blong proton we i ODD mo wan nomba blong neutron we i ODD i stap wetem INTEGER spins.

<p>True</p> Signup and view all the answers

Ol niuklies we i gat wan nomba blong proton we i ODD, o wan nomba blong neutron we i ODD, i stap wetem HALF-INTEGER spins.

<p>True</p> Signup and view all the answers

Ol niuklies i stap wetem charge.

<p>True</p> Signup and view all the answers

Wanem saens we ol charge i stap tekem?

<p>Ol charge we i stap muv i stap mek wan fild blong magnetik.</p> Signup and view all the answers

Ol niuklies we i gat SPIN i no save stap wetem wan fild blong magnetik.

<p>False</p> Signup and view all the answers

Wanem saens we i stap yusum blong lukluk long fild blong magnetik blong niuklies?

<p>Wan arrow.</p> Signup and view all the answers

Wanem saens blong niuklies we i stap long normal kondisan?

<p>Ol niuklies i stap fri blong stap long wan spesifik saens long olgeta.</p> Signup and view all the answers

Ol niuklies we i stap long olgeta, i stap wetem wan fild blong magnetik, olgeta i stap long wan saens we i no save stap.

<p>False</p> Signup and view all the answers

Wanem saens we ol niuklies i stap long wan fild blong magnetik?

<p>SPIN state.</p> Signup and view all the answers

Ol niuklies i save stap long wan besik nomba blong SPIN state.

<p>True</p> Signup and view all the answers

Ol niuklies we i stap long wan SPIN state i stap wetem wan spesifik energi.

<p>True</p> Signup and view all the answers

Wanem nomba blong SPIN state we i stap long wan niuklies we i gat saens blong SPIN 1/2?

<p>2</p> Signup and view all the answers

Ol niuklies i stap long wan besik nomba blong SPIN state we i stap moa strong long olgeta.

<p>True</p> Signup and view all the answers

Ol niuklies i save kasem energi we i stap moa strong long olgeta.

<p>True</p> Signup and view all the answers

Wanem saens we ol niuklies i stap kasem taem we olgeta i stap kasem energi we i stap moa strong long olgeta?

<p>Resonance.</p> Signup and view all the answers

NMR i save lukluk long wan spesifik saens blong atom.

<p>True</p> Signup and view all the answers

Wanem informesen we NMR i save givim?

<p>NMR i save givim informesen long saens blong chemikal shift, intensity, lineshape, mo spin-spin splitting.</p> Signup and view all the answers

Wanem saens blong chemikal shift?

<p>Chemikal shift i stap mak long frekwens blong wan signal blong NMR.</p> Signup and view all the answers

Olgeta proton i stap wetem wan frekwens blong resonance.

<p>False</p> Signup and view all the answers

Wanem saens blong chemical shift blong wan proton?

<p>Chemikal shift blong wan proton i stap mak long saens blong atom we i stap long niuklies. Saens ia i save stap lukluk long saens blong ol electron blong atom.</p> Signup and view all the answers

Ol atom we i gat wan nomba blong proton we i ______ i stap wetem wan chemical shift we i defren.

<p>defren</p> Signup and view all the answers

Ol niuklies i save kasem wan energi we i defren we i stap mak long frekwens.

<p>True</p> Signup and view all the answers

NMR i save lukluk long ol sampl we i stap long air.

<p>True</p> Signup and view all the answers

Wanem ol sampl we NMR i save lukluk long olgeta?

<p>NMR i save lukluk long ol sampl we i stap long air, mo i save lukluk long ol sampl we i stap long solusen, o solid.</p> Signup and view all the answers

NMR i save lukluk long ol sampl we i stap long air, mo i save lukluk long ol sampl we i stap long solusen, o solid. Olgeta sampl ia i stap long air, solusen, o solid.

<p>True</p> Signup and view all the answers

Study Notes

NMR Principle

  • NMR stands for nuclear magnetic resonance
  • A nucleus of an atom is placed in a magnetic field and exposed to electromagnetic radiation
  • It resonates at a specific frequency of radiation
  • This specific resonance frequency is used for analysis

Electromagnetic Spectrum

  • Shows different types of electromagnetic radiation
  • From long wavelengths (radio waves) to short wavelengths (gamma rays)
  • NMR uses radio frequency (RF) radiation

Nuclei with Spin

  • Nuclei with an odd number of protons and/or neutrons have a property called spin
  • Spin is a fundamental characteristic
  • Only nuclei with spin are detectable by NMR
  • These nuclei are called 'spin active' or 'NMR active'
  • Nuclei with even numbers of both protons and neutrons do not have spin and are 'NMR inactive'

Properties of Spin

  • Spin is a fundamental property of nature
  • Unpaired electrons, protons, or neutrons have a spin of 1/2
  • Nuclei have spin determined by the number of protons and neutrons
  • Nuclei with odd numbers of protons or neutrons have half integer spin
  • Nuclei with even numbers of both protons and neutrons have integer spin
  • The nuclear spin quantum number has values of 0, 1/2, 1, 3/2, etc...

Nuclear Precession in a Magnetic Field

  • In the macroscopic world, magnets can be aligned in infinite orientations
  • At the atomic level, these alignments are quantized and the number of orientations is (2I + 1) where I = spin value
  • We primarily deal with spin 1/2 nuclei
  • Different orientations have different energy levels determined by Zeeman splitting

Zeeman Splitting

  • Energy levels are determined by the external magnetic field strength
  • Nuclei with different orientations have different energies
  • When a magnetic field (Bo) is applied, different energy differences result based on the possible spin directions

Number of Spin States

  • The total number of spin states available is 2I +1 (where I is the spin value)
  • Many common nuclei have spin- 1/2 (hydrogen, carbon-13, etc. )

Spin States in an Applied Magnetic Field

  • Nuclei in an external magnetic field align against (higher energy) or with (lower energy) the field
  • Conventionally, the applied magnetic field (Bo) is applied along the z-axis

NMR Absorption

  • Nuclei can only absorb energy that matches the energy difference (ΔE) between spin states
  • This absorption causes resonance, creating a peak on the NMR spectrum.

NMR Observables

  • NMR experiments provide information about spin populations: -Chemical shift: signal frequency -Intensity: strength of the signal proportional to the population of spins -Lineshape : information about the population homogeneity -Spin-spin splitting: information about nuclei connected by chemical bonds

The Chemical Shift

  • The resonant frequency of a nucleus is affected by the local electronic environment.
  • This difference in frequency based on environment is chemical shift.
  • Chemical shift is measured in parts per million (ppm) relative to a reference compound (usually tetramethylsilane TMS)
  • Chemical shift (δ) = (measured frequency shift in Hz / spectrometer operating frequency in Hz) × 106

Ring Current Shifts

  • Aromatic nuclei like benzene rings create a ring current which affects the magnetic field experienced by nearby protons, causing them to resonate at higher frequencies (deshielded) resulting in a downfield shift

Spin-Spin Couplings - Scalar Coupling

  • Equivalent protons do not split each other
  • Protons farther away than three bonds generally do not split one another
  • The number of splits depends on the number of neighboring protons

Origin of Spin-Spin Splitting

  • Spin-spin coupling arises from interaction between the spins of neighbouring nuclei, causing a splitting into multiple signals.
  • The number of signals resulting from the splitting follows Pascal's triangle.

NMR Sensitivity

  • NMR requires relatively high sample concentrations.
  • 100 μM concentration is preferred. Other nuclei require higher concentrations while 1H is generally available in sufficient quantities.

Applications of NMR

  • Used for studying diverse substances including small molecules, macromolecules, molecules in solutions, and solids
  • Versatile tools for research, analysis, and in healthcare and many other industries

Instrumentation

  • NMR experiments use sophisticated equipment including a powerful magnet, radio frequency coils, and a computer system for data analysis
  • Typically, the spectrometer is surrounded with liquid nitrogen and helium to maintain extremely low temperatures for effective performance - often found in shielded environments

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Quiz blong NMR principle mo ol proprieties blong spin. Diswan i lukim hao NMR i wok mo wanem ol naet i fit long NMR analysis. Yu mas save wetem ol naet long spin mo hem i impoten blong NMR.

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