lecture 2 - Organic Lecture Series CH 310 N LECTURE 2...

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Organic Lecture Series 1 CH 310 N LECTURE 2 Textbook Assignment: Chapter 13 (NMR) Homework (for credit): To be Posted NEXT week Today’s Topics: NMR-introduction & theory Notice & Announcements: 1) T 1) Text Problems posted to WEB (optional) 2) +/- system for letter grades will NOT be used this semester. Organic Lecture Series 2 OH H 2 SO 4 Major + Minor Reactions will often give a mixture of products: How would the chemist determine which product was formed? How would the chemist determine which product was formed? Both are Both are cyclopentenes cyclopentenes ; they are isomers. ; they are isomers. Spectroscopy will provide the solution. Spectroscopy will provide the solution.
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Organic Lecture Series 3 Molecular and atomic transitions occur & are frequency dependent. Organic Lecture Series 4 N N uclear uclear M M agnetic agnetic R R esonance esonance Chapter 13 Chapter 13
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Organic Lecture Series 5 Molecular Spectroscopy Molecular Spectroscopy Nuclear magnetic resonance (NMR) Nuclear magnetic resonance (NMR) spectroscopy spectroscopy : a spectroscopic technique that gives us information about the number and types of atoms in a molecule, for example, about the number and types of – hydrogen atoms using 1 H-NMR spectroscopy – carbon atoms using 13 C-NMR spectroscopy – phosphorus atoms using 31 P-NMR spectroscopy Organic Lecture Series 6 • An electron has a spin quantum number of 1/2 with allowed values of +1/2 and -1/2 – this spinning charge creates an associated magnetic field – in effect, an electron behaves as if it is a tiny bar magnet and has what is called a magnetic moment • The same effect holds for certain atomic nuclei – any atomic nucleus that has an odd mass number, an odd atomic number, or both also has a spin and a resulting nuclear magnetic moment – the allowed nuclear spin states are determined by the spin quantum number, I , of the nucleus Nuclear Spin States Nuclear Spin States
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Organic Lecture Series 7 Nuclear Spin States Nuclear Spin States – a nucleus with spin quantum number I has 2 I + 1 spin states; if I = 1/2, there are two allowed spin states – Table 13.1 gives the spin quantum numbers and allowed nuclear spin states for selected isotopes of elements common to organic compounds 1 H 2 H 12 C 13 C 14 N 16 O 31 P 32 S Element Nuclear spin quantum number ( I ) Number of spin states 1/2 1 0 0 0 1/2 1 23 1 2 1/2 21 Organic Lecture Series 8 Nuclear Spins in Nuclear Spins in B 0 – within a collection of 1 H and 13 C atoms, nuclear spins are completely random in orientation – when placed in a strong external magnetic field of strength: B 0 , however, interaction between nuclear spins and the applied magnetic field is quantized, with the result that only certain orientations of nuclear magnetic moments are allowed (can occur)
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Organic Lecture Series 9 –for 1 H and 13 C, only two orientations are allowed E = h ν Organic Lecture Series 10 • In an applied field strength of 7.05T, which
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This note was uploaded on 11/21/2011 for the course CH 51455 taught by Professor Colapret during the Spring '11 term at University of Texas at Austin.

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lecture 2 - Organic Lecture Series CH 310 N LECTURE 2...

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