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| Arrhenius equation | predicts that the rate of reaction increases if the temperature is raised. link |
| Aspirator | is a device that produces vacuum by means of the Venturi effect. In an aspirator, fluid (liquid or gaseous) flows through a tube which then narrows. When the tube narrows, the fluid's speed increases, and because of the Venturi effect, its pressure decreases. Vacuum is taken from this point. |
| Atropisomer | is a stereoisomer that results from hindered rotation about a single bond where the steric strain barrier to rotate is high enough to isolate the different conformers i.e., ortho-substituted biphenyls or binaphthalenes (i..e, BINAL) link |
| Auxochrome | is a substituent that increases absorption of a molecule of a methyl, hydroxyl, alkoxyl or amino group or a halogen atom. If the auxochrome is conjugated with a π-electron system, the λ-max value is shifted to a longer wavelength (bathochromic) link |
| Beer-Lambert-Law | is the basic law for all absorption processes (A=εcl). It states that the absorbance of a sample is directly proportional to the concentration of the solute in the sample, the path length and the molar extinction coefficient (ε). The law only applies for much diluted solution (c<10-4 mol/L) link |
| Bathochromic shift | is a shift to higher wavelength in the UV-Vis spectrum (increased λ-value) link |
| Boiling point | is the temperature when a liquid becomes a gas. It depends highly on the surrounding pressure. A lower surrounding pressure results in a lower boiling point (i.e., vacuum distillation) link |
| Bredt's Rule | is an empirical observation that states that a double bond cannot be placed at the bridgehead of a bridged ring system, unless the rings are large enough. This is the reason why only one isomer of norbornene exists. link |
| Catalyst | is a compound that increases the rate of the reaction by lowering the activation energy for a chemical reaction, but does not change the yield. link |
| Chromatography | is a technique to separate compounds from each other. It is based on the distribution various compounds between the mobile phase and the stationary phase. link |
| Chromophore | is a chemical group that absorbs light at a specific wavelength and so imparts color to a molecule i.e., carbonyl group or azo group. link |
| Condensation point | is the temperature at which the conversion of a substance from the vapor state to a denser liquid or solid state takes place usually initiated by a reduction in temperature of the vapor. link |
| Coupling constant | characterizes the line spacing (in Hz) within a multiplet in a 1H-NMR spectrum, which permits conclusions about the distance and the angle of interaction of the coupling partners. Decant(ing) the process in the laboratory when a liquid is transferred into a different container and the solid is left behind. link |
| Dew point | the temperature at which a vapor begins to condense (which is not equal to the boiling point!). link |
| Diastereomer | is a stereoisomer of a compound having two or more chiral centers that is not a mirror image of another stereoisomer of the same compound. link |
| Disproportionation | refers to the transformation of a substance into two or more dissimilar substances usually by simultaneous oxidation and reduction i.e., Mn(III) forms Mn(II) and Mn(IV). link |
| Distillation | is a technique to purify (primarily) liquids based on their different boiling points. link |
| Distribution coefficient | also called partition coefficient. Quantifies the distribution of a compound between two different phases (K=c1/c2). The distribution coefficient between octanol and water is often referred to as log Kow. link |
| Emulsion | is a suspension of finely divided particles in a continuous medium in which the particles are approximately 5 to 5,000 Å in size, do not settle out of the substance rapidly, and are not readily filtered i.e., oil and vinegar in a vinaigrette, or fat in water in milk. link |
| Enantiomer | is a molecule that is not superimposable on its mirror image, related to chirality. link |
| Enantiomeric Excess | is the ratio of one enantiomer to the other enantiomer in a mixture (abbreviated: e.e. or ee). It is often used in context of asymmetric synthesis. Related: diastereomeric excess. link |
| Exclusion rule | describes the fact that a molecule with a center of inversion has peaks either in the infrared or in the Raman spectrum, but not in both. link |
| Extraction | is a process to isolate a compound from a mixture by either temporary chemical modification or distribution within two layers. link |
| FID | =Flame Ionization Detector, a detector used in gas chromatography, very sensitive but destroys the sample due to combustion. link |
| Freezing point | is the temperature at which a liquid becomes a solid. Its depression can be used to determine the molecular weight of compounds (=colligative property). link |
| Hammond Postulate | If two states, as for example, a transition state and an unstable intermediate, occur consecutively during a reaction process and have nearly the same energy content, their interconversion will involve only a small reorganization of the molecular structures. That is, along the reaction coordinate, species with similar energies also have similar structures. link |
| Heterogeneous | is a system that consists of at least two phases (solid-liquid). link |
| Homogeneous | is a system that consists of only one phase. link |
| HOMO | is the highest occupied molecular orbital in a molecule. link |
| Hygroscopic | is a compound that absorbs water from the air or a solution, nature of drying agents. link |
| Hyperchromic | refers to an increased absorption of UV-Vis light (increased ε-value). link |
| Hypochromic | refers to a decreased absorption of UV-Vis light (decreased ε-value). |
| Hypsochromic shift | is the shift to lower wavelength in the UV-Vis spectrum (decreased λ-value). link |
| In-situ | refers to the synthesis of a reactive intermediate, which is not isolated since it is too difficult or too dangerous. link |
| Infrared spectrum | is a spectroscopic technique to identify functional groups, looks at vibrational modes of the molecule. The modern instruments are FTIR instruments. link |
| Lachrymator | a compound that makes the eyes fill with tears but does not damage them ("teargas") i.e., bromoacetone. link |
| Le Châtelier Principle | describes equilibrium reactions and how to influence them by introducing stress. link |
| Lock-and-Key method | describes the selectivity of enzymes towards certain substrates over others. link |
| LUMO | lowest unoccupied molecular orbital. link |
| Melting point | is the temperature at which a solid becomes a liquid, usually reported as a range (=lower number is the temperature when the solid starts to melt, the upper number is the temperature when the entire sample melted). If the sample decomposes, it should be noted as "dec." in parenthesis. link |
| Metalorganic | a compound that possesses carbon but no direct M-C bond i.e., sodium acetate, Jacobsen's catalyst, etc. |
| Methylene chloride | =dichloromethane link |
| Mobile Phase | is a term used in chromatography. It consists usually of an organic solvent (or mixture) in column chromatography. link |
| Mother Liquor | the solution that was separated from the crystals. link |
| Neat | a term often used in infrared spectroscopy, means that only the pure compound was place in the infrared beam. |
| NMR spectroscopy | is a spectroscopic technique to identify functional groups and structure of a compound. It looks at behavior of nuclear spins in an external magnetic field, frequently used as 1H or 13C-NMR spectroscopy in organic laboratories. link |
| Oligomer | is a polymer or polymer intermediate containing relatively few structural units (more than two units). link |
| Organometallic | the compound has at least one metal-carbon bond i.e., Grignard reagent, ferrocene, etc. link |
| Petroleum ether | (also called petrolether or ligroin) is a mixture of different hydrocarbons. The name does not refer to oxygen containing compounds but much more on its volatility. It is available in different boiling point ranges i.e., 30-60 oC, 60-90 oC, 100-140 oC. link |
| Polymorphism | describes the ability of a solid to exist in different crystalline forms i.e., silica, TiO2, etc. link |
| Pyrolysis | is the process where organic compounds decompose when heated without burning. link |
| Pyrophoric | means that a compound catches on fire when it comes in contact with air. Many finely divided metal powder or strong reducing reagents react like this i.e., Grignard reagents, organolithium compounds, Raney Nickel, LiAlH4. link |
| PTC | =Phase Transfer Catalysis, utilizes a catalyst which is able to transport an ion from one phase (usually aqueous) into the other phase (organic). link |
| Quenching | a reaction is terminating by deactivating reactive intermediates. link |
| Racemic mixture | that is composed of equal amounts of dextrorotatory and levorotatory forms of the same compound and is not optically active. link |
| Recrystallization | is a technique used to purify solids based on different solubilities of the impurity and the target compound. link |
| Reflux | implies that a solution/solvent is heated to a boil while maintaining its volume constant. This is usually accomplished by using a device to catch the solvent vapors i.e., condenser. link |
| Refractive Index | is a physical property that quantifies the refraction of light by a solid or liquid. It highly depends on the temperature and the wavelength it is observed. link |
| Retardation factor | is the ratio of how far the center of a spot traveled compared to the solvent front (=Rf-value). link |
| Retention time | is the time interval that passed between the sample injection and the appearance of the peak maximum. link |
| Rinsing/Rinse | refers to the washing of a solid with small amounts of cold solvent to remove mother liquor and impurities from the surface. |
| Saturated Solution | is a solution that contains the maximum amount of solute at a given temperature. link |
| Seeding | is a technique to initiate crystallization from saturated or super-saturated solutions. link |
| Solvatochromism | the change of a compounds color due to the solvent polarity i.e., Brooker merocyanine. link |
| Split-mode | refers to the fact that only a small amount of the sample is actually introduced to the GC column. link |
| Stationary Phase | is a term used in chromatography. It refers to the part, which absorbs the compound. The stronger the interaction is, the longer the compound requires moving through the column. link |
| Stevenson Rule | states that when a fragmentation takes place in mass spectrometry, the positive charge remains on the fragment with the lowest ionization energy. link |
| Sublimation Point | is the temperature at which a solid evaporates without melting first. link |
| Superheating | the process at which a liquid is heated above its boiling point without vaporization. Can be avoided by adding boiling stones, boiling sticks or a spin vane. link |
| Supersaturated | is a solution that contains more than the maximum amount of solute at a given temperature. Often causes problems during the recrystallization process. link |
| TCD | =Thermal Conductivity Detector, less sensitive than FID, but allows to collect sample. link |
| Trituration | commonly refers to the grinding of powders in a pestle or mortar. It is a method to induce crystallization of a pure compound from impure oil or the process of separating two solids by selectively dissolving one compound while the other is insoluble. link |
| UV-Vis spectroscopy | is a technique to investigate conjugation within molecules. Often used for colored compounds. Looks at the excitation of electrons from a bonding to an anti-bonding orbital. link |
| Vacuum filtration | is a filtration technique that permits to separate a solid from a liquid. The vacuum increases the flow rate of the mother liquor through the filter paper. Not suitable for low boiling or hot solvents! link |
| Washing | is a process to remove small amounts of byproducts or a catalyst from a reaction mixture. link |
| Zaitsev's Rule | predicts the formation of an alkene based on thermodynamic stability: the alkene with the highest the degree of substitution is preferentially formed under thermodynamic conditions. link |