Quantitation, additives

Noth. The above method can be successfully applied only to dilute solutions of formaldehyde which are free in particular from other alfphatic aldehydes, since the latter, if present, would undergo a similar oxidation. Formaldehyde, if mixed with other aldehydes, should be estimated by quantitative addition of potassium cyanide for details, see advanced text-books of quantitative organic analysis. 

Titration An analytical method involving the quantitative addition of reagents to a solution until an endpoint is reached as indicated by a color change or a precipitate. 

A characteristic reaction of sulfmylimines RNSO is the quantitative addition of R Li reagents to form adducts of the type Li[RNS(R )NR]. ° The structures of these sulfmimidinates are discussed in Section 10.4.4." The reactions of RNSO derivatives with two equivalents of lithium tert-butylamide result in the formation of diazasulfite anions [OSNR(N Bu)] (9.12) (Eq. 9.12)." The dilithium derivatives of these dianions form hexameric thirty-six atom (Lii2Ni206S6) clusters with structures that are dependent on the nature of the R group. 

The facile quantitative addition of mercaptoethanol 200 d onto the double bonds of bicyclopropylidene derivatives has successfully been applied to separate the difluorocarbene adduct 122 from the starting material 121 (see Scheme 24) [116]. 

Gaseous HCl adds to maleimide (134). Even more general are quantitative additions of HBr, which succeed with maleimide (134), maleic anhydride, fu-maric acid (28), and maleic acid [28]. 

Scheme 12. First, quantitative addition of to-furan functionalized PIB (A ), obtained from a simple reaction between living PIB and 2-BusSnFu, to living PIB (A) could be achieved in Hex/CH2Cl2 (40/60 v/v) at -80 °C in conjunction with TiCl4. The resulting living coupled PIB-Fu+-PIB was successfully employed for the subsequent chain ramification polymerization of MeVE. This technique has its unique ability to control A and A block length independently. Pure poly(IB-s-IB -s-MeVE) three-arm star-block copolymer was obtained upon purification of the crude product by column chromatography [87].

The acidifying effect of the nitro group is so profound that very mild bases can be used to catalyse the reaction. This enables selective removal of the proton next to the nitro group and helps to avoid side-reactions involving aldol condensations of the carbonyl component, Common examples include amines, quaternary ammonium hydroxides, and fluorides, Even basic alumina is sufficient to catalyse virtually quantitative addition of this benzylic nitroalkane to cyclohexenone at room temperature ... 

Based on these considerations, the following 2 minimal quality criteria for low-dose mixture experiments suggest themselves for assessments of studies published in the literature 1) The effects of individual mixture components should have been determined under conditions similar to those of the mixture. 2) NOAELs (or NOELs and NOECs when a neutral effect concept is adopted) should have been estimated for each mixture component, and the absence of observable effects demonstrated directly. In addition to these 2 minimal requirements, it would be desirable to calculate quantitative additivity expectations. This would allow evaluations of combination effects in terms of synergism, antagonism, or additivity. 

Lithiated enol carbamates 559 have been reported as complementary acyl anion equivalents of MVL (524) and EVL (525). Non-fluorinated enol carbamates have been prepared by O-carbamoylation of acetaldehyde lithium enolate (80-87% yield) or by quantitative addition of trimethylsilylamides to vinyl chloroformate837. 

The Lewis bases for each of the superacid systems are the conjugate bases of the acids themselves, namely F, SO3F- and CF3SOJ. If enhanced basicity of one of the acids is required for specific speciation of a solute in a synthetic reaction, for example, it is easily achieved by direct quantitative addition of the base F, SO3F and CF3SO3 as the appropriate alkali metal cation or ammonium salts which dissociate completely in these media of high dielectric constant. 

Activity ratios A=R/R(j were found Table 1) where is the rate on the unpoisoned surface. A drop in activity is observed for addition of Li, F% or Na it appears that the drop in activity is smoother in the case of Li, less smooth for F, and initially rather sleep for Na. Quantitatively, addition of 1 mmol of either of those ions to Ig of Y-AI2O3 decreases A to... 

Crotylboronic esters (2-butenylboronates) are thermally stable and isolable compounds at room temperature and undergo nearly quantitative additions to aldehydes. The required crotylboronic esters may be prepared by reaction of the crotyl potassium reagents derived from cis- or trans-2-butene with n-butyllithium and potassium tert-butoxide followed by addition of the appropriate trialkyl borates. ... 

Although MALDI applications for quantitative analysis of biopolymers have been shown recently, most applications involve qualitative studies [21—23]. Limitations in the quantitative addition of matrix to analyte and online configurations of MALDI, compared to gas chromatography/MS and liquid chromatography (LC)/MS systems, have kept the primary focus on qualitative applications. 

A similar system with additional strain on the cyclopropane ring is quadricyclane. Its reaction with benzeneselanyl chloride in apolar solvents gave quantitatively addition products with preference for the formation of stereoisomeric 3-chloro-2-phenylselanylbicyclo[2.2.1]hept-5-enes 4 and 5. In polar or protic solvents such as acetonitrile, methanol or acetic acid, the competing opening of only one of the cyclopropane rings became dominant. The benzeneselanyl cation cleaved the most strained C — C bond in cyclopropane with concomitant or subsequent reaction with a nucleophilic solvent molecule. ... 

Matrix components are not efficiently removed with protein precipitation and will be contained in the isolated supernatant or filtrate. In MS/MS detection systems, matrix contaminants have been shown to reduce the efficiency of the ionization process with atmospheric-pressure ionization (API) techniques [3-12]. The observation seen is a loss in response, and this phenomenon is referred to as ionization suppression. This effect can lead to decreased reproducibility and accuracy for an assay and failure to reach the desired limit of quantitation. Additionally, the efficiency of protein removal witli organic solvents is not complete and typically ranges from 98.7% to 99.8% [2] to leave residual amounts of protein that carry over into the analytical system and foul the ionization source of a mass spectrometer after repeated injections. 

DPL-Cholesterol System. The increase of film pressure with the quantitative addition of a DPL solution in chloroform-methanol (85 15) on the surface of 0.15M NaCl shows a typical surface saturation curve (Figure 9). Surface viscosity increased with each addition and with film... 

Actinide hydrides are rather hydridic and undergo rapid reactions typical of such systems for example, reactions with ketones and halocarbons provide actinide alkoxides and halides, respectively. Rapid quantitative addition of terminal alkenes (the reverse of jS-hydride elimination) is consistent with the known bond disruption enthalpies (equation 66). ... 

Ground crystals of A -viiiylplitlialimide 1 (100 mg, 0.58 mmol) were exposed to HBr gas (100 mL, 1 bar). The excess gas was evacuated after 30 min and a quantitative yield of 2b was obtained. HCl and HI reacted similarly to give 2a and 2c, while tlie quantitative addition of Br2 took 16 h to produce quantitatively 2d. 

The quantitative addition of benzylamine to 391 provides /S, 0-benzylglyceraldimine (407), which undergoes Grignard addition to afford a mixture of threo-40S and erythro-409 amino alcohols. The product ratio obtained depends on the solvent and metal cation employed. Addition of cerium(III) chloride in THE reverses the stereoselectivity in favor of the erythro adduct 409 [137]. 

---