Advantages And Disadvantages Of Hydroxybutyrate

Melting Point Data Table Compound Aspirin Caffeine Salicylamide Actual MP (ºC) 93 - 98 260 - 262 96 - 102 Expected MP (ºC) 135 236 140 Percent Error (%) ~30% ~12% ~30%

CHE 135 Experiment 2, General Chemistry III Lab, Spring Quarter 2015-2016, DePaul University. [Online] htps://www.d2l.depaul.edu (April 19, 2016).

After the process of recrystallization was completed, the melting points and weights were taken for each solid. Some melting points recorded for the solids were very close to the values listed in the literature. However, others differed by sizeable margins from the values listed in the literature. The range observed for the melting point of naphthalene was 78-81°C. This coincides with

The objectives in this laboratory were to be able to calculate the freezing point depression among three trials of unknowns, be able to correctly measure the freezing points of p-xylene, and to be able to calculate the molar masses of the unknowns by found freezing point depression values. This was done to be able to understand and apply a concept names supercooling. Supercooling is when a liquid is put far under its original freezing point and remains a liquid or gas. This happens when a substance is cooled so quickly that it’s easier for it to stay a liquid than to crystalize, until it reached its nucleation point and begins to heat up returning to its freezing point (image 4). The supercooling of p-xylene was observed in three

The melting point of a compound is used by organic chemists not only to identify the compound, but also to establish its purity. To determine the melting point two temperatures were noted. The first was the point at which the first drop of liquid formed among the crystals; the second was the point at which the whole mass of crystals turned to a clear liquid. And the melting point was recorded from this

Nanocrystals are made up of drug with only little amount of surfactant (below critical micelle concentration (CMC)) to stabilize formulation [14]. Most of the nanoparticles are made up of large amount of excipients which is not the case with nanocrystals as most of the part is only the drug. Besides lower amount of stabilizers makes toxicity issues associated with nanosuspensions negligible and offers ease of scale-up and better physical stability compared to amorphous form [15, 16]. Different methods are classified as top-down (high pressure homogenization, media milling, and sonication) and bottom-up techniques (nanoprecipitation) for effective production of Nanocrystals [17]. Development of nanocrystal based formulation of risperidone can be advantageous to tackle the problem of poor water solubility. Numerous solidification techniques are used to increase physical stability of nanosuspensions as spray drying, lyophilization and many more based upon the properties of drug and characteristics of final formulation. Amongst all these techniques lyophilization is used predominantly for nanosuspension solidification.

In order to discover the melting point range of Unknown 33A, a Digimelt was utilized. Melting point is the temperature at which a crystalline structure changes from solid to liquid. By adding thermal energy, the structure changed from solid to liquid. The thermal energy increased the kinetic energy, which then overcame the intermolecular attractive forces between the molecules. This increase in speed allowed the molecules to move more freely. By identifying the melting point range of Unknown 33A, it narrowed the possibilities of the unknown by ruling out the compounds with melting points greater than ± 20°C from Unknown 33A’s melting point range.

The next day the micro-melting point was taken using a Stanford Research System Optimelt Automated Melting Point System. Finally, a small amount of crystals were ground up with a mortar and pestle, mixed with one drop of Nujol mull (GLR), and placed on a sodium chloride window which was used to obtain a FT-IR spectrum on a Perkin-Elmer Paragon 1000 FT-IR.

Our results lead us to think that the possible reason for this low percentage, as well as for the differences between melting point range obtained and the actual melting point (128- 130 ° C 0 ° C instead of 135- 136 ° C) might have been due errors in the time that the re-crystallized sample spent in the oven. This theory is reinforced by

[2] Skoog, D. A., West, D. M., Holler, F. J., & Crouch, S. R. (2014). Fundamentals of analytical chemistry (Ninth ed.) Brooks/Cole, Cengage Learning.

In order to achieve the best result, this experiment was broken into two part: the first part of this experiment involves carrying out solubility tests on known compounds, N-pivaloyl-o-toluidine, and in the second part the TLC and solubility tests was used to find a suitable recrystallization solvent for an unknown compound. For Experiment 6A, a 50 mL round-bottom flask with a small stir bar and septum was flame-dried under the hood, and cooled down to room temperature. Then, a balloon was filled with N2 and attached to the rubber septum in the round-bottom flask via a 20G, ½ needle. The flask was clamped to a stir plate and 9.3 mL of DCM was cautiously added using a 12 mL syringe and a long thick needle. Furthermore, 1.2 mL of pivaloyl chloride was added to the mixture using a 3 mL syringe and a 22G‚1/2 needle. Next, the flask was carefully submerged into an ice and water bath for 15 minutes until the

The physicochemical properties of nanoparticles that have been identified as important factors in uptake and toxicity include crystal structure, size, surface charge, surface energy, and chemical composition [14].

The HDI/PCN/BD stoichiometric ratio for the synthesis of the final polymer was kept as 4:3:1. The polymer solution was passed through a Teflon filter in order to

The isoelectric point of the stained peroxidase bands where determined by comparing their migration distances with known isoelectric points of standard

The melting point range was close to the anti structure, but because it was a widened range it is speculated that the syn structure was also present. (Q9) However, this does not mean the other mechanisms are completely discarded. Upon recrystallizing the pure product, a gross mistake potentially skewed the results; non-DI water from the ice bath was introduced to the crystallized product by mistake. Recrystallization of the pure product was redone, but random ions from the ice bath could have infiltrated the crystal lattice of the pure product thereby widening the melting range. Also, the melting range could have been affected by the temperature intervals used; time was running out and the Digi-Melt was programmed to increase in intervals of 10°C instead of 5°C. This could have affected the melting range observed significantly; slow and steady probes to be a better method. (Q10) Both the percent yield (106.5%) and recovery (54.75%) are not ideal numbers; ideally, percentages should be close to 100% but not over or under. As mentioned above, (in Q9), a gross mistake occurred where non-DI water got into the pure product as it was recrystallizing; the flask’s buoyancy caused it to tip over and the non-DI water from the ice bath got inside the pure product. This affected the data as electrolytes from the ice bath could now be part of the crystal lattice of the pure