pH and pKa

pH and pKa: Chapter 2: A molecule or an atom group in a molecule may lose or gain a proton when the molecule is placed in an aqueous solution The exact probability that a molecule will be protonated or deprotonated depends on the pK a of the molecule and the pH of the solution Let AH be an atom group in a molecule AH may be neutral or charged After AH loses a proton it is denoted by A

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Amino groups: NH2 or NH3+?

07/06/2009The Amino group: NH2 has to be bonded to another group to satisfy the valence of the nitrogen which is 3 ie R-NH2 where R is another group NH2 alone would imply the anion (NH2)-Following on from the above there is a lone pair of unbonded electrons on the nitrogen atom This lone pair can be protonated by H+ to give: R-NH3+ an ammonium cation

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Acids and Bases

Chemists use pKa values to discuss relative acidities of protic acids We will: 1) reexamine how one experimentally determines a pKa value 2) determine the direction/shift of an acid/base equilibrium 3) examine pKa values for various protic functional groups CH 3CO 2H+ H2O H3 O– + + cid Base Conj ugate base ConjgateAcid Keq Cl B Cl Cl O C H3CCH3 + 9/4/2015 Determination of pKa Discussing pKa

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Les Acides Amins

Les fonctions COOH et NH2 sont les uniques fonctions ionisables des AA Chaqune s'ionise de la faon suivante: En solution un AA peut exister sous plusieurs ionisations en fonction du pH de la solution A+ A+/-A-Un AA ne peut exister en solution que sous une de ces trois formes ci-dessus Donc la forme NH2-CH-COOH avec le radical est la forme dite solide Quand le pH du milieu est infrieur

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What is the pKa of water?

The value of 14 0 for the pKa of water at 25C has been experimentally measured 3 4 This value can also be obtained by the same process used to calculate the pKa of all other water-soluble compounds that can act as acids in aqueous solution: from the analysis of thermodynamic or electrochemical data for these aqueous solutions The origin of the value of 15 7 for the pKa of water is

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Acidity and Basicity of Drugs

to phenyl group are better donating groups by induction (more available lone pair of electrons) the lone pair of electrons are not available delocalized through the phenyl group (stable by resonance) NH2 NH3 NH NH2 pKa = 0 5 pKa = 9 0 H Which one is the stronger base? pKa = 0 5 Ka = 10-0 5 NH2 NH3 NH [ Ph2 NH ][ H ] Ka [ Ph2 NH 2 ] Ka NH2 pKa = 9 0 H Ka = 10-9 1 100 5 [ PhCH 2

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Determination of pKa of ammonium and phenolic groups

The pKa values of some compounds containing ammonium phenolic and both ammonium and phenolic or ammonium and methoxy groups have been determined The results and probable explanations are described herein Experimental The compounds 3H 4H and 5H were commercial products of highest available purity All other chemicals used were also of reagent grade Synthesis of N-(2′

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Biochem Question

31/08/2010The aminoacid glycine is often used as the main ingredient of a buffer in biochemical experiments The amino group of glycine which has a pKa of 9 6 can exist either in the protonated form ( -NH3+) or as the free base (-NH2) because of the reversible equilibrium R-NH3+ R-NH2

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Substituent effects on the physical properties and pKa of

The aniline molecule is nonplanar with its NH2 group lying at an angle of approximately 42 to the plane of the benzene ring Substituents on the phenyl ring alter this out-of-plane angle as well as other molecular properties such as the ring bond lengths and angles the barrier to inversion Einv a nd the pKa of the amino group

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What's the difference between the amino groups NH2 and

04/10/2011If you protonate an amino group -NH2 you get an ammonium ion -NH3+ Which form - the weakly basic amino group or its conjugate acid the ammonium ion depends on the pKa of the amino group and the pH of the surrounding medium For example the amino groups in amino acids will be protonated at physiological pH (and the acid groups will be

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Amines diamines and cyclic organic nitrogen compounds

Phenyl: An phenyl group is a benzene substituent missing one hydrogen with general formula C 6 H 5 Amine: A compound or functional group that contain a basic nitrogen atom with a lone pair It can be a primary (R-NH2) a secondary (R' R''-NH) or a tertiary amine (R' R'' R'''-N) where R represent an alkyl or other organic substituent For 1

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Which Of The Following Is True With Respect To The Pka

Why is the pKa of an NH2 group of amino acid lower than an NH2 group of primary amines? The question implies that an amino acid is more acidic than the relative amino acid This is because when a carboxylic group is attached it exerts a electron pulling effect ie The -COOH group will exert a -I effect This will lower the availability of the

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basic pKa's

11/12/20069 0 is related with aromatic nitrogen and -2 is related with NH2 For HPO4(2-) and HS(-) you were lucky because macro and micro specieses are the same In other words macro inonization steps are the same than micro ionization step This is why you were able to explain well your basic acidic definition with microspecies However for [NH3+]c1ccncc1 molecule macro and micro species are

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What Is The Pka Of Arginine Physical

The pKa of the acid group is around 2 5 and that of the ammonium group is around 10 Arginine being a basic amino acid bears cationic charge below pK 2 — 9 04 so has strong affinity for hair at pH over about 4 the isoelectric point of hair (6) Values for the negative logarithm of the acid dissociation constant pKa of inorganic acids and bases as well as hydrated metal ions

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Organic Functional Groups:

Organic Functional Groups: Aldehydes ketones 1 alcohols etc (Indonesian Polish Translations of this page) Organic chemistry is dominated by the functional group approach where organic molecules are deemed to be constructed from:An inert hydrocarbon skeleton onto which functional groups (FGs) are attached or superimposed

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Amino Acid pI Question

11/09/2014If the pH is 6 and since the pKa of the amino terminus is 9 then we'd have 1000:1 times more of the NH3+ form over the NH2 form which for all intents and purposes is NH3+ We relate the carboxyl group in a similar way to pH keeping in mind the log-based relationship and HH equation Finding the pI is useful because it tells us when the species on average is in it's neutral form

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Biochem Question

31/08/2010The aminoacid glycine is often used as the main ingredient of a buffer in biochemical experiments The amino group of glycine which has a pKa of 9 6 can exist either in the protonated form ( -NH3+) or as the free base (-NH2) because of the reversible equilibrium R-NH3+ R-NH2

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Acids and Bases 2 HCl 3 H20 4 H30+

NH3 asanacid NH3 + HO:- :NH2 + H20: NH3 asabase + NH3 + HBr: NH4 +:Br: 3 a The lower the pKa the stronger the acid so the compound with apKa =5 2 is the stronger acid b The greater the dissociation constant the stronger the acid so the compound with an acid dissociation constant =3 4 X 10-3 isthe stronger acid 4 pKa = 4 82 therefore K

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