Determination Of An Unknown Amino Acid From Titration

Below is a free term papers summary of the paper "Determination Of An Unknown Amino Acid From Titration." If you sign up, you can be reading the rest of this term papers in under two minutes. Registered users should login to view this term paper.

Term Paper Title	Determination Of An Unknown Amino Acid From Titration
# of Words	1807
# of Pages (250 words per page double spaced)	7.23

Determination of An Unknown Amino Acid From Titration

Determination of An Unknown Amino Acid From Titration

Abstract

     Experiment 11 used a titration curve to determine the identity of an
unknown amino acid.  The initial pH of the solution was 1.96, and the pKa’s
found experimentally were 2.0, 4.0, and 9.85.  The accepted pKa values were
found to be 2.10, 4.07, and 9.47.  The molecular weight was calculated to be
176.3 while the accepted value was found to be 183.5.  The identity of the
unknown amino acid was established to be glutamic acid, hydrochloride.

Introduction

     Amino acids are simple monomers which are strung together to form polymers
(also called proteins). These monomers are characterized by the general
structure shown in figure 1.

     Fig. 1

Although the general structure of all amino acids follows figure 1, the presence
of a zwitterion  is made possible due to the basic properties of the NH2 group
and the acidic properties of the COOH group.  The amine group (NH2) is Lewis
base because it has a lone electron pair which makes it susceptible to  a
coordinate covalent bond with a hydrogen ion.  Also, the carboxylic group is a
Lewis 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 or
basic salts.  For example, if the glycine reacted with HCl, the resulting amino
acid would be glycine hydrochloride (see fig. 2). Glycine hydrochloride is an
example 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 a
basic salt form.

     Fig. 2

     Fig. 3

Due to the nature of amino acids, a titration curve can be employed to identify
an unknown amino acid. A titration curve is the plot of the pH versus the volume
of titrant used.  In the case of amino acids, the titrant will be both an acid
and a base.  The acid is a useful tool because it is able to add a proton to the
amine group (see fig. 1).  Likewise the base allows for removal of the proton
from the carboxyl group by the addition of hydroxide.  The addition of the
strong acid or base does not necessarily yield a drastic jump in pH.  The acid
or base added is unable to contribute to the pH of the solution because the
protons and hydroxide ions donated in solution are busy adding protons to the
amine group and removing protons from the carboxyl group, respectively.  However,
near the equivalence point the pH...

This is not the end of the termpaper! Register below to see the complete version of this term paper.

Membership Plans	Credit Card	Check

1 month membership

3 month membership (You Save 50%)

6 month membership (You Save 67%)

Copyright © 2002-2007 Mid Term Papers. All rights reserved. This term papers website is used for research purposes only.
If you have forgotten your username or password, please click here.
If you like to cancel your account, please click here.

1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22