Determination Of An Unknown Amino Acid From Titration Essay -- essays

Determination of An Unknow Amino Acid From Titration hoistExperiment 11 use a titration turn off to determine the indistinguishability of anunknown amino assembly acid. The initial pH of the solution was 1.96, and the pKas embed experimentally were 2.0, 4.0, and 9.85. The accepted pKa values werefound to be 2.10, 4.07, and 9.47. The molecular cant was calculated to be176.3 while the accepted value was found to be 183.5. The personal identity of theunknown amino acid was established to be glutamic acid, hydrochloride. debutAmino acids are simple monomers which are strung together to trope polymers(also called proteins). These monomers are characterized by the generalstructure shown in figure 1.     Fig. 1Although the general structure of all amino acids follows figure 1, the presenceof a zwitterion is made possible due to the basic properties of the NH2 groupand the sulfurous properties of the COOH group. The amine group (NH2) is Lewisbase because it has a lone electron pair which makes it sensitised to acoordinate covalent bond with a enthalpy ion. Also, the carboxyl group is aLewis acidic because it is able to donate a hydrogen ion (Kotz et al., 1996).Other forms of amino acids also exist. Amino acids may exists as acidic orbasic flavors. For example, if the genus Glycine reacted with HCl, the resulting aminoacid would be glycine hydrochloride (see fig. 2). Glycine hydrochloride is anexample of an acidic salt form of the amino acid. Likewise, if NaOH were added,the resulting amino acid would be sodium glycinate (see fig. 3), an example of abasic salt form.     Fig. 2     Fig. 3Due to the nature of amino acids, a titration curve can be employed to identifyan unknown amino acid. A titration curve is the plot of the pH versus the volumeof titrant used. In the case of amino acids, the titrant will be both an acidand a base. The acid is a useful tool because it is able to add a proton to theamin e group (see fig. 1). Likewise the base allows for removal of the protonfrom the carboxyl group by the sum of hydroxide. The addition of thestrong acid or base does not unavoidably yield a drastic jump in pH. The acidor base added is unable to contribute to the pH of the solution because theprotons and hydroxide ions donated in solution are busy adding protons to theamine gr... ...unded series of crude estimates which wererequired. Likewise, the deflection of the calculated molecular weight can beattributed to these crude vehicles, because the budge in volume (between comparability points) were used in calculation.ConclusionThe identity of an unknown amino acid was determined by establishing atitration curve. The comparison and half-equivalence point, the pKa values,and the molecular weight were directly or indirectly found by the titrationcurve. The equivalence points were found through a crude method known as thetrapezoidal method. The establishment of the equivalence point s gave rise tothe half equivalence points and the D volume (used in calculating the molecularweight). The half-equivalence points were directly used to find the pKa valuesof the unknown. The molecular weight could also be calculated. This info led tothe determination of the identity of the unknown amino acid--glutamic acid,hydrochloride.ReferencesJicha, D. Hasset, K. Experiments in full general Chemistry Hunt Dubuque, 199137-53.Kotz, J.C. Treichel , P. Jr. Chemistry and Chemical Reactivity Harcourt-Brace assemble Worth, 1996 816-     837.