Tài liệu, ebook Khoa Học Tự Nhiên

Nuclear Magnetic Resonance Imaging is a noninvasive diagnostic tool. “Nuclear” is omitted because of public’s fear that it would be radioactive. Computer puts together “slices” to get 3-D images. Tumors are readily detected.

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Isotopes are present in their usual abundance. Carbon has a 13C isotope present in 1.1% abundance. The spectrum will show the normal M+ and small M+1 peak. Bromine has two isotopes: 79Br (50.5%) and 81Br (49.5%). Since the abundances are almost equal, there will be an M+ peak and and M+2 peak of equal height.

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Easy for inorganic salts: CrO42- reduced to Cr2O3. KMnO4 reduced to MnO2. Oxidation: Gain of O, O2, or X2; loss of H2. Reduction: Gain of H2 (or H-); loss of O or O2; and loss of X2. The gain or loss of H+, H2O, HX, etc. is neither an oxidation nor a reduction.

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The thiolate will attack the carbon displacing the halide. This is an SN2 reaction so methyl halides will react faster than primary alkyl halides. To prevent dialylation use a large excess of sodium hydrosulfide with the alkyl halide.

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Permanganate Oxidation of Alkynes to Carboxylic Acids If potassium permanganate is used under basic conditions or if the solution is heated too much, an oxidative cleavage will take place and two molecules of carboxylic acids will be produced

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An alkene (monomer) can add to another molecule like itself to form a chain (polymer). Three methods: Cationic, a carbocation intermediate Free radical Anionic, a carbanion intermediate (rare)

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Use concentrated sulfuric or phosphoric acid, remove low-boiling alkene as it forms to shift the equilibrium, and increase the yield of the reaction. Carbocation intermediate: 3º alcohols react faster than 2º. Primary alcohols are the least reactive. Rearrangements are common. Reaction obeys Zaitsev’s rule.

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Brønsted-Lowry bases are H+ acceptors any material that has atoms with lone pairs can potentially be a Brønsted-Lowry base because of the molecular structure, often one atom in the molecule is more willing to accept H+ transfer than others NH3(aq) is basic because NH3 accepts an H+ from H2O, forming OH–(aq) water acts as acid, donating H+

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Strength of the nucleophile determines order: Strong nucleophiles or bases promote bimolecular reactions. Primary halide usually undergo SN2. Tertiary halide mixture of SN1, E1 or E2. They cannot undergo SN2. High temperature favors elimination. Bulky bases favor elimination.

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when the solute-to-solvent attractions are weaker than the sum of the solute-to-solute and solvent-to-solvent attractions, the solution will only form if the energy difference is small enough to be overcome by the entropy

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