Although now both the tannins salt and caffeine are water soluble, using an organic solvent, dichloromethane, renders tannins salt insoluble. Caffeine is more soluble in dichloromethane (14g/100g) than in water (2g/100g). Caffeine will dissolve in the dichloromethane phase while tannins salts remain in the aqueous phase. Addition of sodium sulphate will act as a drying agent and evaporation of the dichloromethane solution would yield pure caffeine which is white in
12. The TLC data obtained is provided in a table below. The TLC data was conducted solely in a 9:1 hexane/ethyl acetate solvent solution as opposed to the 1:1 and pure hexane solution as well. This was due to the lack of time, but as explained in number 7, a very polar solvent (1:1 solution) or non-polar solvent (pure hexane) is not ideal when obtaining
Many compounds decompose at the temperatures required for efficient GC separation while HPLC separation can be achieved readily. However, GC is particularly useful in detecting residual solvents in formulations and is also invaluable in looking for degradation products. Amines and acids are not separated well by GC because they tend to be too polar. SPECTROSCOPY Spectroscopy is a technique that is used for the detailed analysis of the compound and its structure prediction. There are various techniques: UV-SPECTROSCOPY: Ultraviolet–visible spectroscopy refers to absorption spectroscopy or reflectance spectroscopy in the ultraviolet-visible spectral region.
This helps to indicate whether or not the reaction follows Markovnikov’s Rule, which states that the electrophile (E+) will add to the carbon involved in a double bond that produces the most stable carbocation. If the rule is followed, the reaction will proceed according to the mechanism in Figure 1. In the silver nitrate test, the alkyl bromide is added to AgNO3. The rate of precipitation with 2° should be faster than the solution with the 1° alkyl halide. In the sodium iodide test, the alkyl halide is added to sodium iodide in acetone.
One noticeable exception is the so-called “Atwal modification” of the Biginelli reaction. In this scheme, an enone(a) is first condensed with a suitable protected urea or thiourea derivative(b) under almost neutral conditions. Deprotection of the resulting 1,4-dihydropyrimidine(c) with HCl or TFA leads to the desired DHPMs.20 Scheme-3: Shutalev et al described another approach to DHPMs synthesis. This synthesis is based on the condensation of readily available R-tosylated (thio)ureas(a) with the enolates of acetoacetates or 1,3-dicarbonyl compounds. The resulting hexahydropyrimidines(b) need not to be isolated and can be converted directly into DHPMs.
The second is that we assumed the density of our citric acid monohydrate solution was 1.06 g/mL. Again, depending on what the actual density of our solution was, it could skew the result. My two values for the change in enthalpy, -118.21 and -155.31 kJ, don’t necessarily agree with each other, but do not completely disprove one another. One possible experimental error is that the magnetic stir bar that was placed into the solutions may not have always been spinning. In the beginning trials, it was very inconsistent.
This causes the indicator to change colour due to the colour difference from the undissociate molecules. Strong acids and strong bases are strong electrolytes and are assumed to ionize completely in the presence of water. Weak acids however, only ionize to a limited extend in water. Any weak or strong acids when in contact with any weak or strong alkali will start to undergo neutralization regardless of their volume. When an indicator which is present in the acid-base mixture and have experienced colour change, it indicates that the mixture is in right proportions to neutralize each other and is also known as the equivalence point.
The melting points for the acidic and neutral compounds were hence too low, and the melting point for the basic compound was too high. The errors in the acidic and neutral compounds can be explained by impurities in the crude product, along with the presence of the solvents, ethyl acetate and water, which disturbed the stability of the compounds, and led to lower melting points over a larger range. The abnormally high melting point of the base may have been observed due to improper separation of the acid and base solutions in the separation funnel. Some of the acidic compound may have entered the basic solution and reacted with the base to form a high melting point salt, making the melting point of the base appear abnormally high. The Mel-Temp was also turned on a high setting accidentally, so it is possible that the temperature rose too quickly to get a good reading of the melting
Pioneering work by Ackermann et al disclosed that less expensive ruthenium complex also can catalyze the isoquinolone synthesis from benzamides with alkynes.24 The reaction of N-substituted benzamides with internal alkynes in the presence of [RuCl2(p-cymene)]2 with Cu(OAc)2.H2O as an oxidant afforded isoquinolones with good substrate scope (Scheme 1.17). The reaction works well with both symmetrical and unsymmetrical alkynes, and in case of unsymmetrical alkynes highly regioselectivity was achieved. Following this report, the same group discovered a green protocol for the synthesis of isoquinolones from N-methoxybenzamides in water (Scheme 1.18).25 In this reaction, carboxylate salts are used as additives along with the ruthenium complex. The green protocol was viable with free hydroxamic acids also. Li et al also reported the synthesis of isoquinolone motif using N-methoxybenzamides 1.60 under mild reaction conditions in the presence of ruthenium catalyst without using any external oxidant.26 Here C-H bond functionalization occurs at room
First of all, the reactant ethyne used in all of the reactions was the product of another reaction between water and calcium carbide. However, due to the fact that neither the calcium carbide nor the water can be guaranteed to be pure, the reaction to produce ethyne may have created other unwanted by-products. Additionally, as ethyne itself is very reactive, the possibility exists that some ethyne may have reacted with the waste products to create new, unwanted compounds, further reducing the experiment’s accuracy by adding contaminants. In addition, when the result of the combustion reaction of ethyne is being observed, it is important to ensure any observations, specially the smell and smoke produced, are created by the reaction and not from burning the wooden spit, which also generates smell and smoke, especially when it is extinguished. This can be remedied by extinguishing the spit away from the test tube at a place that is not upwind of the
Xylene was used as a solvent that provided a quicker way of reaction between the two starting materials. The Diels-Alder reaction is stereospecific with respect to both the diene and the dienophile. A cis-dienophile gives cis-substituents in the product and a trans-dienophile gives trans-substituents. If the diene substituents have the same stereochemistry, the diene substituents would be on the same face of the product. If the diene substituents have opposite stereochemistry, the diene substituents would be on opposite faces of the product.