<p class=\"MsoNormal\" style=\"margin-bottom: 0.0001pt; text-align: justify;\"><span style=\"font-size: 12.0pt; font-family: \'Times New Roman\',\'serif\';\">The properties of xanthine and its derivatives are of interest due to their biological and pharmaceutical importance. They are purine base, found in most human body tissues, fluids and tea, coffee, cocoa and cola drinks.&nbsp; They have pharmacologic properties that stimulate the central nervous system and relax smooth muscles.&nbsp; Further, they are used in the synthesis of organic biochemical and drugs. The hydroxyl substituted derivative of xanthine namely hypoxanthine is used in the biochemical research and it contain both a pyrimide ring and an imidazole ring. It is naturally occurring purine derivative known as 6-hydroxypurine and found as a constituent of nucleic acids. The understanding of its structure, molecular properties as well as nature of reaction mechanism has great importance and has been the subject of many experimental and theoretical studies. Hence, the detailed theoretical investigation of the title compound has been undertaken by computationally. </span></p>
<p class=\"MsoNormal\" style=\"margin-bottom: 0.0001pt; text-align: justify; text-indent: 0.5in;\"><span style=\"font-size: 12pt; font-family: \'Times New Roman\', serif;\">Geometry optimization is one of the most important steps in the theoretical calculations. The model molecular structure of </span><span style=\"font-size: 12.0pt; font-family: \'Times New Roman\',\'serif\';\">hypoxanthine l was built in gauss-view 05 <span style=\"color: #231f20;\">and </span>was used to optimize the structure. The molecules under investigation have been analyzed with density functional theory (DFT), employing Becke&rsquo;s three parameter hybrid exchange functionals with Lee-Yang-Parr correlation functionals (B3LYP) with 6-311++G(d,p) basis set. All the calculations were performed using the Gaussian 09 program. In this study the&nbsp; density functional theory (DFT) were used to determine the relative energies, electronegativity(&chi;), hardness (&eta;), softness(S), electrophilicity index (&omega;) and local reactivity descriptors such as Fukui function, for the hypoxanthine isomers (H1,H2,H3,H4,H5 and H6). The local reactivity has been analyzed through the condensed Fukui function using natural population analysis (NPA). All calculations were performed using the Gaussian 09 program.</span></p>
 
<p class=\"MsoNormal\" style=\"margin-bottom: 0.0001pt; text-align: justify;\"><strong><span style=\"font-size: 12.0pt; font-family: \'Times New Roman\',\'serif\';\">Key words:</span></strong><span style=\"font-size: 12.0pt; font-family: \'Times New Roman\',\'serif\';\"> Hypoxanthine, DFT, Gaussian 09, HOMO-LUMO, hardness, softness, Fukui function.</span></p>