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Topic: Protic solvent


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  Process for preparing a sulfate ester of a polyhydroxy polymer - United States Patent 4,177,345
To the suspension of the polyhydroxypolymer(s) in one of the specified solvents or solvent mixtures, enough dinitrogentetroxide and/or nitrosylchloride is added in gaseous or liquid form or as a solution preferably in one of the previously mentioned solvents to obtain a highly esterified nitrite ester of the polyhydroxypolymer(s).
In this case, the acidic catalyst is added to the protic solvent to be used subsequently for the regeneration of the polyhydroxypolymer and the separation of the polymer mixture in the form of certain shaped articles.
As already mentioned, the choice of the protic solvent depends on the polymer mixture, and it should be selected in such a way that, on contact, regeneration of the polyhydroxypolymer and separation of both the polyhydroxypolymer and the polymer lacking hydroxyl groups occur essentially simultaneously.
xrint.com /patents/us/4177345   (15247 words)

  
 Solvent - Wikipedia, the free encyclopedia
Solvents should therefore not react chemically with the dissolved compounds — they have to be inert.
Solvent vapors can also form in supposedly empty drums and cans, posing a flash fire hazard; hence empty containers of volatile solvents should be stored open and upside down.
Solvents are often refluxed with an appropriate desiccant prior to distillation to remove water.
en.wikipedia.org /wiki/Solvent   (1507 words)

  
 cars - Solvent
Solvents usually have a low boiling point and evaporate easily or can be removed by distillation, thereby leaving the dissolved substance behind.
Solvents should therefore not react chemically with the dissolved compounds - they have to be inert.
Solvents can also be used to extract soluble compounds from a mixture, the most common example is the brewing of coffee or tea with hot water.
www.carluvers.com /cars/Solvent   (885 words)

  
 Solvents   (Site not responding. Last check: 2007-10-11)
The solvent also provides a means of temperature control, either to increase the energy of the colliding particles so that they will react more quickly, or to absorb heat that is generated during an exothermic reaction.
The polarity of the polar protic solvents stems from the bond dipole of the O-H bond.
Non-polar solvents are compounds that have low dielecrtic constants and are not miscible with water.
www.usm.maine.edu /~newton/Chy251_253/Lectures/Solvents/Solvents.html   (643 words)

  
 Method for enhancing gas well secondary recovery operations - Patent 6622790
A protic solvent may be defined as a solvent which readily accepts or donates a proton during a chemical reaction.
A protic solvent employs an acidic hydrogen that is attached to an oxygen or nitrogen molecule to tear apart ionic compounds such as Iron II chloride and Iron III chloride, one of the "salts" commonly found in gas wells and formations.
One may determine that the target solvent capacities for either the protic or aprotic solvents and solutes may be increased or decreased accordingly for different operational conditions as is known to those of ordinary skill in the art.
www.freepatentsonline.com /6622790.html   (4329 words)

  
 U.S. Patent: 6143359 - Soluble metal hydride/transition metal dichalcogenide alloys - November 7, 2000
The replacement of the protic solvent is crucial to the alloying of organic-solvent soluble metal hydrides with single molecular layer transition metal dichalcogenides and for the inclusion of other materials that react in a detrimental manner with protic solvents.
Alternatively, if the aprotic solvent selected has a boiling point at a temperature higher than the protic solvent used as a carrier, than the suspension may be heated to remove the protic solvent.
Alternatively, the protic solvent may be replaced with a miscible aprotic solvent by adding a material dissolved within the replacement aprotic solvent, which reacts with protic solvent.
www.everypatent.com /comp/pat6143359.html   (2585 words)

  
 GALLIC ACID, Acido Gálico
In low polarity and non-protic solvents GA fluorescence is characterized by enhance in the fluorescence quantum yield and a blue shift in the emission maximum, however, in dioxane its behavior is closer to those observed in protic solvents.
In dioxane, the solvent with the lowest dielectric constant, 2.2, the maximum is shifted to 268 nm compared to 260 nm in water, in alcohols to 271 nm and to 267 nm for acetonitrile, a nonprotic solvent with dielectric constant close to that of methanol.
In protic solvents where efficient hydration of GA molecule occurs the steric hindrance is canceled by the attached solvents molecules what efficiently dissipate excitation energy and even for anionic form the fluorescence quantum yield is low.
taninos.tripod.com /acidogalico.htm   (6122 words)

  
 Preparation of 4,4'-dihydroxy-'alkylstiblbene with reduced dimer formation - Patent 5723692
The process of claim 5 wherein the volume-to-volume ratio of the polar protic solvent to water is not less than 4:1, and the concentration of the halogenated intermediate is sufficiently low such that the yield of 1,2,4,5-tetrakis(4-hydroxyphenyl)-4-pentenes does not exceed about 0.5 percent at a complete conversion of the halogenated intermediate.
The process of claim 1 wherein the halogenated intermediate and the water-immiscible solvent is added gradually to a preheated solution containing the water and the polar protic solvent, so as to increase the effective dilution of the halogenated intermediate in the water and the polar protic solvent.
The polar protic solvent is used in a sufficient amount to form a substantially uniform dispersion of the components, preferably throughout the course of the conversion of the halogenated intermediate.
www.freepatentsonline.com /5723692.html   (4042 words)

  
 U.S. Patent: 5541051 - Preparation of silver halide tabular emulsions in the presence of polar aprotic solvents and/or ...
In order to stabilize the precipitated silver halide grain nuclei addition of a protective colloid apart or together with at least one protic solvent or with a mixture of at least one protic and at least one aprotic solvent is required.
Preferred protic solvents are water and (lower) alcohols as, e.g., methanol and ethanol.
During the optionally present growth step(s) following further in partially protic solvent mixtures in the same or in a reaction vessel different from the one in which twinned nuclei were initiated before, an increasing flow rate of aqueous silver nitrate and aqueous alkali metal halide solutions is preferably applied, e.g., a linearly increasing flow rate.
www.everypatent.com /comp/pat5541051.html   (3546 words)

  
 Wilmad-Labglass :: NMR-004: Sample Solvents in NMR Spectroscopy
In addition, the isotopic purity of deuterated solvents, which easily degrade through exchange with the protons in water in the atmosphere, must be maintained at high levels.
Choosing the correct isotopic purity of deuterated solvent in proton NMR is also critical to avoid excessive protic solvent signals.
Combinations of protic and deuterated solvent are frequently used to control solvent costs while providing a sufficient source of deuterium lock signal.
www.wilmad-labglass.com /services/NMR_004.jsp   (797 words)

  
 Alkanes oxidation
O-donor ligated complexes may have the potential for higher thermal, protic and oxidant stability given the expected covalent character of oxygen-metal bonds with the late transition metals and the lower basicity of oxygen.
These complexes are highly air and protic solvent stable and show catalytic exchange between alkanes/ arenes (methane, cyclohexane, n-octane, benzene, acetone) and protic solvents such as triflouroacetic acid, acetic acid, benzene, methanol and water.
This is an important result as it shows that the CH activation chemistry as well as the thermal stability to air and protic media of O-donor, late transition metal complexes are not unique to the acac-O,O complex and secondly, that the chemistry of O-donor, late-transition metal complexes can be significantly changed by ligand modification.
www-rcf.usc.edu /~rperiana/index_files/Page1143.htm   (611 words)

  
 Reference.com/Encyclopedia/Protic solvent
In chemistry any solvent that carries hydrogen attached to oxygen as in a hydroxyl group, nitrogen as in an amine group, or, more generally, any molecular solvent which contains dissociable H
Polar aprotic solvents are solvents that share ion dissolving power with protic solvents but lack an acidic hydrogen.
These solvents generally have high dielectric constants and high polarity.
www.reference.com /browse/wiki/Protic_solvent   (156 words)

  
 section3.htm
It is shown that the most important parameter determining the magnitude of the solvent induced shift in –C=O stretching band is the ability of the solvent to interact with the solute as a Lewis acid.
Thus, when the aprotic solvent is dissolved as a dilute solute in a second solvent, the solvent induced frequency shift, SIFS, may be used to characterize the intermolecular interactions.
In the aqueous MeCN solvent system, it is possible to predict that urea residues in the aqueous structure as both sides of the urea molecule are preferentially solvated by water.
www.ijvs.com /volume5/edition6/section3.html   (1604 words)

  
 CHEM 331, Organic Chemistry I   (Site not responding. Last check: 2007-10-11)
Solvents: Wide variety can be used, but polar, aprotic solvents (see end of Handout) are favored and usually cause 2° halides to react by this mechanism.
Solvents: Wide variety can be used, but polar, protic solvents (see end of Handout) are favored and usually cause 2° halides to react by this mechanism.
Solvents: Reaction is favored in polar, protic solvents.
www.towson.edu /~ryzhkov/handouts/SEhand.html   (1486 words)

  
 [No title]   (Site not responding. Last check: 2007-10-11)
\par \tab Because polarity is the most important factor in determining how a solvent works, you need to look up the toxicity of each of the solvents and indicators, and in the hand book of chemistry and physics, look up the polarity (dipole moment) of each of the solvents.
Allow the solvent to rise until it is about 1cm from the top of the sheet.
\par }{\f37\fs20\cf1\insrsid16318472 \tab Produce a table showing the three}{\f37\fs20\cf1\insrsid11997957\charrsid16318472 solvents and the three indictors and show the distances moved by the indicators and the solvent and the value for the retentions factor in each box.
www.uwrf.edu /~kp0b/chm789/exercises/TLC.doc   (857 words)

  
 section2.htm
This is the mean equilibrium constant, K*, for the replacement of one component of the mixed solvent by the other in the coordination shell of the chromophore.
For TMU molecule in aqueous MeCN and DMSO solvent systems, this change in solvent shell composition is reflected in a change in the position of –C=O stretch band in the IR spectra.
Where A represents the solute and H and S are the mole fraction of protic (water) and aprotic components of the mixed solvent respectively.
www.ijvs.com /volume6/edition2/section2.html   (1556 words)

  
 Project 1: Room Temperature Ionic Liquids
We were one of the early groups involved in these studies noting that the transition metal catalysts are retained in the RTIL and thus both solvent and catalyst can be recycled a number of times.
Not only does this decrease the amount of solvent waste that is generated, it also enables the reuse of expensive transition metal catalysts and ligands.
In particular, two classes of RTILs have been developed: a nucleophilic solvent based on nicotine and a protic solvent based on fructose.
www.chem.binghamton.edu /HANDY/greenpage.htm   (1454 words)

  
 CONTINUATION OF SUBSTITUTION; ELIMINATION
Since ions benefit greatly from solvation by polar solvents, it is clear that an increase in the solvent polarity will yield an increased stabilization of the TS (compared to the energy of the reactant halide, which is moderately polar, but not ionic), thus greatly increasing the rate.
The dilemma is solved by using what is called a "dipolar aprotic solvent", i.e., a solvent which is polar enough to dissolve the salt well, but does not have an acidic hydrogen to stabilize the nucleophile.
DMSO is a polar solvent because the S-O bond is highly polar, very close to ionic, because to form a pi bond with oxygen (i.e.
research.cm.utexas.edu /nbauld/teach/ch8/elim.html   (1602 words)

  
 SNTWO
Protic solvents tend to surround anything that is positive or negative.
Therefore the protic solvent will surround the nucleophile and form a cage around it.
If the nucleophile is surrounded by a cage formed by the protic solvent it is going to have a difficult time coming in and attacking the carbon.
www.organicchemistryreview.com /SNTWO.html   (1306 words)

  
 SN1 Reactions
Polar Protic solvents are solvents in which at least one Hydrogen atom is bonded to either an Oxygen or an Nitrogen.
Polar Aprotic solvents are solvents whose molecules exhibit a molecular dipole moment but whose Hydrogen atoms are not bonded to an Oxygen or Nitrogen atom.
This represents an excellent solvent for a substitution that is occuring in the SN path.
members.aol.com /logan20/sn1.html   (1299 words)

  
 Orgo Question - Student Doctor Network Forums
the aprotic solvent is bulky, and the positive dipole is blocked by steric hinderence.
Thus, Sn2 rxn's favor a polar aprotic solvent, that doesn't have a partial positive charge on an easily accessible, small, H atom.
Common polar protic solvents are OH groups...water and low-molecular-weight alcohols.
forums.studentdoctor.net /showthread.php?t=174757   (690 words)

  
 sn1
Remember that protic solvents tend to surround anything that is positive or negative.
Even if the nucleophile is surrounded by a cage formed by the protic solvent it doesn't matter.
If the hill is made into a smaller one (as it is when an SN1 reaction is run in a protic solvent) then the reaction is run much faster because it takes a shorter amount of time to cross a smaller hill.
www.organicchemistryreview.com /sn1.html   (1433 words)

  
 [No title]   (Site not responding. Last check: 2007-10-11)
Chemists place solvents into one of three classifications: polar protic, polar aprotic (sometimes called dipolar), and non-polar.
A polar aprotic solvent contains a heteronuclear double bond such as C=O or S=O, but does not contain an OH group.
A non-polar solvent is one that does not contain the polar groups that characterize polar protic and polar aprotic solvents.
www.usm.maine.edu /~rhodes/252/text/U1/U1Pre.doc   (860 words)

  
 Patent 6,066,619
The present invention provides stable non-aqueous formulations which are solutions of peptide compounds in non-aqueous protic solvents.
In yet a further aspect, the invention provides methods for treating a subject suffering from a condition which may be alleviated by administration of an peptide compound, said methods comprising administering to said subject an effective amount of a stable non-aqueous formulation comprising at least one peptide compound in at least one non-aqueous protic solvent.
A method for treating a subject suffering from a condition which may be alleviated by administration of a peptide compound comprising administering to said subject an effective amount of a stable non-aqueous formulation of a peptide compound comprising:
www.pharmcast.com /Patents/052300OG/6066619_Nonaqueous052300.htm   (375 words)

  
 Equilibria and ChemEquilibria Documentation: Class Solution   (Site not responding. Last check: 2007-10-11)
This constructor assumes the solvent is protic and the user-supplied autodissociation constant is used to construct the autodissociation reaction.
The volume of the solution is adjusted to be consistent with the mass of the solvent and density.
The density is used to calculate a new mass for the solvent.
www.chm.davidson.edu /chemistryapplets/ChemEquilibria/doc/edu/davidson/chm/equilibria/Solution.html   (674 words)

  
 Solvent Effects
1 reaction, the polarity and ability of the solvent to stabilize the intermediate carbocation is of paramount importance, as shown by the relative rate data for the solvolysis of t-BuCl.
2 reaction, the effect of solvent polarity is usually much less, but the ability (or really lack there of) of the solvent to solvate the nucleophile is the important criteria, as shown by the relative rate data for the S
Those species that were most strongly solvated in polar protic solvents will "gain" the most reactivity in polar aprotic (e.g.
mhhe.com /physsci/chemistry/carey/student/olc/ch08solventeffects.html   (324 words)

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