Constitutional isomers 1 have different physical properties that have the same carbon number but different structures. The difference may not be large, but they are found to have different melting points, boiling points, densities, indexes of refraction, and so forth. For example, a branched chain isomer has a lower boiling point than a straight chain isomer. Thus normal pentane has a boiling point of 36 o C, isopentane with a single branch 28 o C, and neopentane with two branches 9.5 o C. This effect of branching on boiling point is observed within all families of organic compounds. It is reasonable that branching should lower the boiling point: with branching the molecular shape tends to approach to that of a sphere and as this happens the surface area decreases, as the result of that the intermolecular forces become weaker and are overcome at a lower temperature. The branching effect on the dynamic properties of liquid alkanes, such as self-diffusion constant, viscosity, and thermal conductivity, is one of the most interesting phenomena. For liquid butane, the experimentally observed behavior 2 tells us that viscosity increases with branching. For liquid pentane, hexane, and heptane, however, branching decreases the viscosity, for example, 0.289 and 0.273 cp at 273.15 K, and 0.240 and 0.223 cp at 293.15 K for normal pentane and isopentane, 0.326 and 0.306 cp at 293.15 K for normal hexane and isohexane, and 0.409 and 0.384 cp at 293.15 K for normal heptane and isoheptane, 3 respectively. These experimental results, except for liquid butane, indicate that as the molecular shape tends to approach that of a sphere and the surface area tends to decrease with branching, the intermolecular forces becomes weaker and the viscosity of alkane isomers decreases. In the present note, we report equilibrium molecular dynamics (MD) simulations for the systems of small normal and isomeric alkanes - normal butane and isobutane, normal pentane and isopentane, and normal hexane and isohexane. The primary study goal is to analyze the diffusion and viscosity dynamics of small normal and isomeric alkanes at different temperatures.