X rays crystallography

17. Aug 2021

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X rays crystallography

  1. X-rays Crystallography Presented by: Jacob Thon Bior Reg No- ND0120003 M. Pharmacy Department Of Pharmaceutical Chemistry KLE College Of Pharmacy, Belagavi. 1 Department Of Pharmaceutical Chemistry
  2. CONTENT: Introduction to x-ray crystallography Production of x- rays Different x-ray methods Bragg’s law Rotating crystal technique X-ray powder technique Types of Crystals Application of x-ray diffraction References 2 Department Of Pharmaceutical Chemistry
  3. Introduction X ray crystallography is an importance tool to identify the atomic and molecular structure of crystal. The crystalline atoms causes a beam of incident x rays to diffract into many direction. Crystallography produce three dimensional picture of the density of electron with in the crystals and from crystal density, the mean position of the atom in crystal can be determine. The intensity of each diffracted ray is fed into a computer, which uses a mathematical equation called a ‘Fourier transform’ to calculate the position of every atom in the crystallized molecule. Department Of Pharmaceutical Chemistry 3
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  5. X-Ray Crystallography is an experimental technique for determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X rays to diffract into many specific directions. The method uses the principle of uniformity of light diffraction of crystals to determine the structure of a molecule or atom. X-ray beam to “hit” the crystallized molecule, the electrons surrounding the molecule diffract as the X-rays hit them. This forms a pattern, this type of pattern is called the X-ray diffraction pattern Department Of Pharmaceutical Chemistry 5
  6. X rays X rays are invisible highly penetrating electromagnetic radiation with short wave length and high frequency than visible light. . The wavelength range for X rays is from about 10-8 m to about 10-11 m, the corresponding frequency range is from about 3 × 1016 Hz to about 3 × 1019 Hz. X-ray technology was invented completely by accident. In 1895, a German physicist “Wilhelm Roentgen” made the discovery while experimenting with electron beams in a gas discharge tube He placed various objects between the tube and the screen, and the screen still glowed. Finally, he put his hand in front of the tube, and saw the outline of his bones projected onto the fluorescent screen. Immediately after discovering X-rays themselves Department Of Pharmaceutical Chemistry 6
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  8. X- RAY PRODUCTION The x-rays are generated when electrons are accelerated under a potential different and turned into electromagnetic radiations. On applying a high voltage by x-ray generator to the cathode as well as anode, the filament and focusing cup determine the path of acceleration. Once high kinetic energy electrons finally reach the anode target, initiating x-ray production. Tungsten is anode target as electrons comes close (As electrons collide with atoms in the target and slow down) to the nucleus of the target leading to deceleration and change in direction converting the kinetic energy to electromagnetic radiation, this process is called breaking radiation the output is spectrum of x-ray energies. 8 Department Of Pharmaceutical Chemistry
  9. X-RAY TUBE The x-ray are generated from x-ray tube of copper cathode and anode with short distance between them, enclose in vacuum and high voltage cable attach to cathode and anode. A filament is heated in cathode ray tube to produce electrons, accelerating the electrons toward the target by applying voltage and bombarding target with electrons, if electrons have sufficient energy to dislodge the inner shell electrons leading to production of x-rays. 9 Department Of Pharmaceutical Chemistry
  10. DIFFERENT X RAY METHODS They are classified into 3 types . X-ray absorption method : In this method ,a beam of x-rays is allowed to pass and the sample which is having the fraction of x-ray photons absorbed is considered for a measurement of the concentration of the absorbing substance .These methods are helpful in elemental analysis . X-ray diffraction method : These methods are based on the scattering of x-rays by crystals .This technique is helpful in identification of crystal structure of various solid compounds. X-ray fluorescence method : In this methods x-rays are generated in the sample and by measuring the wave length and intensity of the generated x-rays , helpful in qualitative and quantitative analysis. 10 Department Of Pharmaceutical Chemistry
  11. BRAGG’S LAW Bragg law identifies the angles of the incident radiation relative to the lattice planes for which diffraction peaks occurs. Bragg derived the condition for constructive interference(interaction of incident ray with sample) of the X-rays scattered from a set of parallel lattice planes. when x- rays are incident on an atom, they make the electronic cloud move as does any other electromagnetic wave. Bragg law is useful for measuring wavelengths and determining the lattice spacing of crystals. To measure a particular wavelength, the radiation beam and the detector are both set at some arbitrary angle θ ....This is a principle on measuring energy of x rays and low energy gamma rays. 11 Department Of Pharmaceutical Chemistry
  12. The relationship between the wavelength of the x ray beam, the angle of diffraction, θ, and the distance between each set of atomic planes of the crystal lattice, d, is given by Bragg’s equation. n λ = 2 d sin θ where, assume n = 1 for the first order reflection λ = wavelength θ = X-ray incidence angle d = distance between atomic layer Department Of Pharmaceutical Chemistry 12
  13. x-ray diffraction: This is phenomena when atomic planes of crystals cause an incident beam of x-ray to interfere with one another as they leave the crystal. It is base on principle that when x-ray are passed on crystal, they get scattered based on the arrangement of atoms in crystal. Department Of Pharmaceutical Chemistry 13
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  15. LAUE METHOD The Laue method is mainly used to determine the orientation of large single crystals while radiation is reflected from, or transmitted through a fixed crystal. The Bragg angle is fixed for every set of planes in the crystal. Each set of planes picks out and diffracts the particular wavelength from the white radiation that satisfies the Bragg law for the values of d and θ involved. Department Of Pharmaceutical Chemistry 15
  16. ROTATING CRYSTAL TECHNIQUE Crystal is rotated about fixed axis, variation in angle θ, the beam is successive diffracted from a given crystal plane whenever in the course of rotation the value of θ satisfies the Bragg equation a spot is produce on photographic plate. 16 Department Of Pharmaceutical Chemistry
  17. X RAY POWDER TECHNIQUE This is rapid analytical technique primarily used for phase identification of crystalline material and provide information on unit cell dimension. The incident monochromatic radiation strikes a finely powdered/homogenized material. In this case, the Bragg angle θ is variable and crystals with the appropriate orientation will give Bragg refraction. 17 Department Of Pharmaceutical Chemistry
  18. Types Of Crystals: Department Of Pharmaceutical Chemistry 18
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  20. APPLICATIONS OF X RAY DIFFRACTION 1. It is primarily used in fundamental science applications for determining the size of atoms, the lengths and different types of chemical bonds, the atomic arrangement of materials, the difference between materials at the atomic level, for determining the crystalline integrity, grain orientation, grain size, film thickness and interface roughness of alloys and minerals. 2. Measurement of sample purity and characterization of organic and inorganic compounds made for pharmaceutical companies. .20 Department Of Pharmaceutical Chemistry
  21. 3. Determining how a drug might interact with specific proteins and how the drug can be improved, analyzing how proteins interact with other proteins, for investigating microstructures, and analyzing what amino acids are present in a protein which can help in determining how catalytically active an enzyme is. 4. Evaluation of physical stability of Amoxicillin trihydrate. 5. X ray Diffraction is used to determination of Cis-Trans isomerism. Department Of Pharmaceutical Chemistry 21
  22. REFERENCES: 1. Instrumental method of analysis by Willard, Merritt, Dean, Settle, CBS Publishers and Distributors, 7th Edition, page NO-340-397. 2. Instrumental methods of chemical analysis by Gurdeep R. Chatwal and Sham K. Anand , Himalaya Publication, 5th revised edition page no. 2.303- 2.339 3. introduction to x ray diffraction#ROTATING-CRYSTAL METHOD. 22 Department Of Pharmaceutical Chemistry