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15 Cards in this Set
- Front
- Back
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Refractometry |
- ratio of speed of light in a vacuum to its speed in the substance - useful for characterizing organic compounds - used to assess purity of known liquids and determine composition of solutions |
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Melting point |
- temp at which solid and liquid phases are in equilibrium at 1 atm - used for identification, characterizing organic compounds and assessing their purity - measured by grinding solid into powder and packing inside melting point tube (capillary tube) - presence of impurities in a substance lowers its melting point and broadens its melting-point range |
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Distillation |
- process of vaporizing a liquid mixture in one vessel and condensing the vapors into another |
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Simple vs. fractional distillation |
Simple - involves a single vaporization-condensation cycle, useful for purifying a liquid that contains either nonvolatile impurities or small amounts of higher or lower boiling impurities Fractional - allows for several vaporization-condensation cycles, useful for separating liquids with comparable volatilities and to purify liquids with large amounts of volatile impurities |
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Two types of filtration |
- Gravity filtration - usually used to remove solid impurities from a liquid or solution - Vacuum filtration - usually used to separate an organic solid from a reaction mixture or a crystallization solvent; removes solid impurities from a large amount of liquid |
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Extraction |
- process of transferring a substance from a liquid or solid mixture to a solvent - used to separate a desired organic substance from a reaction mixture or some other mixture and to remove impurities from a desired organic substance, which is usually dissolved in an organic solvent |
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Evaporation |
- conversion of a liquid to vapor at or below the boiling point of each liquid - used to remove a volatile solvent, such as diethyl ether or dichloromethane from a comparatively involatile liquid or solid - complete solvent removal used to isolate an organic solute after extraction or column chromatography - partial solvent removal (concentration) used to bring a recrystallization solution to its saturation point |
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Recrystallization |
- simplest, most widely used operation for purifying organic solids - dissolves solid that usually had originally crystallized from a reaction mixture or another solution then causing it to crystallize again from solution |
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Heating under reflux |
- Process of boiling a reaction mixture and condensing the solvent vapors back into the reaction - assures that no solvent is lost |
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Mixing |
- used to promote efficient heat transfer, prevent bumping, increase contact between the components of a heterogeneous mixture or mix in a reactant - mechanical stirrer used for viscous liquids or slurries that must be stirred - most common stirring device is stir bar (teflon-coated magnet) |
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Addition of reactants |
- reactants are added during course of reaction when the reaction is strongly exothermic or when one of the reactants must be kept in excess to prevent side reactions - liquids are added in portions or drop by drop using a separators funnel |
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Structures and properties of stereoisomers (optical rotation) |
- Observed rotation: angle by which a sample of an optically active substance rotates the plane of that beam - Polarimetry: measurements of such angles - Polarimeter: instrument that measures these angles - specific rotation of a pure substance can be used to characterize it - [a]=a/lc - enantiomeric excess=[a] observed/[a]pure x 100% - polarimeter has: light source, polarizing prism called a polarizer, a sample cell and another polarizing prism called the analyzer - extinction point: when axis of analyzer is perpendicular to plane-polarized light and light is blocked out so intensity is at a minimum |
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Chain-growth of polymers |
- process in which some monomer molecules are first activated by a polymerization initiator, then monomers are added to its reactive end - addition polymerization: combination of monomer units without eliminating any by-product molecules - step growth polymerization: process in which each polymer chain grows from both ends through a series of individual steps - "tailor-made" polymers with any properties can be made using special catalysts (Ziegler-natta catalysts) to regulate stereochemistry of a polymer and programming sequence of copolymers - condensation polymerization: combination of monomer units containing two or more reactive functional groups that lose a small molecule such as water or HCl |
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Reaction of butanols with Hydrobromic acid |
- codistillation is distillation of two or more non-soluble liquids - steam distillation is when one of liquids is water - steam distillation used to separate organic liquids from reaction mixtures and natural products leaving behind high-boiling residues (tars, inorganic salts) - external steam distillation: carried out by passing externally generated steam into a boiling flask that contains organic material - internal steam distillation: carried out by boiling a mixture of water and an organic material in a distillation setup |
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Drying liquids |
- organic liquids and solutions can be dried in bulk by allowing them to contact with a drying agent - most drying agents are anhydrous (water-free) inorganic salts that form hydrates by combining with water - effectiveness of drying agent depends on: speed, capacity, intensity, chemical inertness, ease of removal - sodium sulfate is drying agent - about 1 g should be used per 25 mL of liquid or 40 mg per mL - using too much results in excessive losses by adhesion of liquid on the drying agent |
