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Qualitative Tests
Published in Thomas J. Bruno, Paris D.N. Svoronos, CRC Handbook of Basic Tables for Chemical Analysis, 2020
Thomas J. Bruno, Paris D.N. Svoronos
Iodoform test: The reagent calls for the mixture of 10 g I2 and 20 g KI in 100 mL water. The reagent is then added dropwise to a mixture of ten drops of the compound in question in 2 mL of water (or dioxane, to facilitate the solubility) and 1 mL 10 % aqueous NaOH solution until a persistent brown color remains (even when heating in a hot water bath at 60 °C). A yellow precipitate is indicative of iodoform (CHI3) formation and is characteristic of a methyl ketone, acetaldehyde, or an alcohol of the general formula CH3CH(R)OH (R = alkyl, hydrogen). Aldols, RC(=O)CH2CH(OH)R', may also give a positive iodoform test by a retro aldol condensation first yielding RC(=O)CH3 and RCHO (detection limit 100 mg). In this case, at least one of the products should be a methyl ketone or acetaldehyde.
Computational Evaluation of Third-Order Optical Nonlinearities
Published in Hari Singh Nalwa, Seizo Miyata, Nonlinear Optics of Organic Molecules and Polymers, 2020
static and dynamic polarizability and hyperpolarizabilities for fluoroform CHF3, chloroform CHCI3, bromoform CHBr3, and iodoform CHI3. All dynamic quantities were calculated at the optical wavelength ?. = 694.3 nm except CHI3 where y(THG) was obtained at 911.3 nm. The frequency-dependent second hypcrpolarizabilities were calculated for optical Kerr effect (OKE) y ( " (">; 0, 0, ?), DC-electric-field- induced second harmonic generation (EFISH) y("2?; 0, ?, ?). third-harmonic generation (THG) ?, ?, ?), intensity-dependent refractive index (IDRI) y(~?; ?, ?, "?) and DC-electric-field- induced optical rectification (EFIOR) y("0; 0, ?, "?). Both a and yincrease in going from fluoroform to iodoform; in particular, yincreases by 2 orders of magnitude. The dispersion of a and yincreases as the atomic number of the halogen atoms in the haloform increases and the dispersion of yin CHI3 increases with an increase in the applied optical frequency. The dispersion of y(EFISH) in CHI3 was larger than that in OKE or IDRI. The CHI3 shows large optical nonlinearities because of polarizable lone-pair electrons of the iodine atoms.
Carboxylic Acids, Carboxylic Acid Derivatives, and Acyl Substitution Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
The iodoform test mixes a suspected methyl ketone with iodine and aqueous hydroxide. The functional group is a methyl group attached to a carbonyl (O=C—CH3). If the methyl ketone functional group is present, a yellow precipitate of iodoform is observed when the ketone is mixed with iodine in aqueous hydroxide. The reaction also works with methyl carbinols that have the structure HO—C—CH3. How are nitriles considered to be carboxylic acid derivatives?
Local structure and orientational ordering in liquid bromoform
Published in Molecular Physics, 2019
Jacob J. Shephard, John S. O. Evans, Christoph G. Salzmann
Trihalomethanes (CHX3) are important in a wide range of environmental settings and industrial applications.[1] To emphasise the chemical similarities with formic acid, they are often called haloforms and can be prepared using the well-known haloform reaction.[2] Fluoroform (CHF3) is a non-ozone depleting greenhouse gas that is used in refrigeration.[3] Both chloroform (CHCl3) and bromoform (CHBr3) are solvents with high densities and are often used for extraction processes. Famous examples include the extraction of morphine from poppies [4] and atropine from thorn apple leaves [5]. Iodoform (CHI3) is solid at room temperature and used as a disinfectant whose distinctive smell is often associated with hospitals. The crystal structure of CHI3 displays disorder with respect to the either parallel or antiparallel alignments of the molecular dipole moments in line with the nonpolar 6/m point-group symmetry of P63/m [6]. Similar types of disorder are also observed for the high-temperature/low-pressure phases of CHBr3 and CHCl3 [7].