LAB+2+Crystallization

Crystallization

Intro:

In organic chemistry, creating a pure solid compound from the process of crystallization is one of the most important  did you not complete your sentence here? . Crystallization is also the general method used for separating two distinct chemical compounds. Laboratory purification of solid crystals involves heating the solid in a selected solvent that is insoluble at room temperature, but is soluble when heated. When solvent cools, the solution will not support the saturation level and crystals of the pure compound will precipitate out. The solution can then be filtered leaving only the pure substance. Solubility tests and crystallization of phthalic acid in water were performed on 10/15/10. During following week, decolorization of Raw sugar and the purification of the Aldol product completed the lab.

Experiments used: Ch 3; 1,2,4 and 7 Williamson K.L., 2003. Macroscale and Microscale Organic Experiments 4th Edition. Boston (MA): Houghton Mifflin Company, p. 38-64
 * Procedure: **


 * Data: **


 * Part I: **
 * Description: **

The solubility test was done at room temperature with the following three different compounds: Resorcinol, Anthracene and Benzoic acid. All of these solutes were mixed with three different solvents: Water, Toluene and Ligroin. Once these ratio mixtures of 10mg solid to .25 ml solvent were made, each solid was observed to be soluble, non soluble, or crystallized. Crystals formed as needles, plates or prisms. It was observed that Resorcinol was soluble and cold to the touch when mixed with water, partially soluble when mixed with Toluene forming plate crystals, and partially soluble with Ligroin forming needle crystals and slightly cool. Anthracene was noted to be generally insoluble in water with little precipitate, partially soluble in Toluene with no crystals but debris at the bottom of the test tube and partially soluble with plate crystals when combined with Ligroin. When Benzoic Acid combined with water it was partially soluble and formed needle crystals, completely soluble when combined with Toluene, and partially soluble with Ligroin forming needle crystals. After observations of solubility were made at room temperature, each mixture that had not dissolved was moved to a hot sand bath then observed. Solutions were omitted from experimentation with heat if they had already been soluble at room temperature. For example, Resorcinol with water and Benzoic Acid with Toluene were not heated. It was noted that Resorcinol and Anthracene heated with Toluene were soluble. Anthracene with water was insoluble with heat and formed prism crystals. Benzoic Acid in water was soluble with the addition of heat


 * **Degree of Solubility ** ||
 * Solution → |||| Water |||| <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Toluene |||| <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Ligroin ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Chemical Compound ↓ || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Cool || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Heat || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Cool || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Heat || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Cool || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Heat ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Resorcinol || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Anthracene || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Insoluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Insoluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Benzoic Acid || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Partially Soluble ||


 * **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Physical Characteristics of Solubility ** ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Solution → |||| <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Water |||| <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Toluene |||| <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Ligroin ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Chemical Compound ↓ || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Cool || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Heat || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Cool || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Heat || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Cool || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Heat ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Resorcinol || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Flat Crystals || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Needle Crystals || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Needle Crystals ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Anthracene || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Flat Crystals || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Flat Crystals ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Benzoic Acid || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Needle Crystals || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">n/a || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Needle Crystals || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Needle Crystals ||

nice job here on the tables.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Compounds Tested: <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;"> <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Recorcinol

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;"> <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Anthracene <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Benzoic Acid

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Crystallization of phthalic acid began with weighing out the compound in solid form. The original weight of the acid before crystallization was 0.060 g. The following proportion was calculated to determine the minimum volume required for crystallization:
 * Part 2: **
 * Description: **


 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 16px;">18 g (X) = .060 mL (100 mL) **

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">The phthalic acid, as water was brought to a temperature of 99 degrees, was estimated to dissolve 0.060 g of compound per 0.333 mL of water. The micro test tube was slowly brought to a near boil then cooled as the solid form of the substance began to dissolve. Repeated alternating of cooling and heating ensured an even separation of solid to liquid. A total of 0.25 mL of water was added during the heating process before all of the phthalic acid completely dissolved.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Following the sand bath heating process, the test tube was corked and allowed to cool at room temperature. Crystallization began almost immediately with spiny needle projections forming at the top and bottom of the liquid acid. The tube was moved to an ice bath to increase the process of crystallization. More rapid formation of crystals occurred at the base of the tube, and the crystals that had formed on the rim of the meniscus began to settle at the bottom of the reaction tube.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Removal of excess water and ethanol with a plastic pipette allowed for a more successful drying process of the crystallized product. The remaining moisture was dried through the glass pipette aspirating vacuum system. Recovery was calculated as follows: There is a problem with sig figs on your calculation. Otherwise the calculation looks good.
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Filter paper and crystals || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">0.158 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Filter paper weight || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">- 0.115 ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Total phthalic acid recovered || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">0.043 +/- .006g ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">% Recovery || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">71.7% ||

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Part 3: <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Description:

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">15.025g of raw sugar were disolved in de-ionized water and heated. The solution was then seperated into two solutions and treated with 250mg and 50mg of de-colorizing charcoal. Once the 250 mg sample of charcoal was added, the solution was heated for two minutes and observed. The solution with 50mg of charcoal was observed after 15 seconds of heating. Samples were then filtered under a hot filtration for a final comparison.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Initial Solution: <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">15.025g Raw Sugar <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">30.000mL D.I. Water

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Initial Solution transfered into augmented solutions: <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">(A) Solution One:
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">1/2 of Initial Solution
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">250 mg decolorizing charcoal

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">(B) Solution Two:
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">1/2 Initial Solution
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">50 mg decolorizing charcoal

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Observations: <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">No noticeable difference in color, consistency or viscosity. Both solutions appeared yellow/brown in color and appeared to have a slightly higher viscosity then water.

<span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">OK: a negative result is still a result. Thanks for doing the experiment.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Part 4: <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Description:

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">The purification of the Aldol product was done through crystallization. A 9:1 EtOH to water solvent was mixed with 0.182 +/-0.002g Aldol reaction product. In order to test solubility, 100 drops of solvent was added to 0.182 +/-0.002g of the solute. Crystals began to change color from a golden yellow to a deep brownish orange liquid. The solution was stirred with a mixing rod to increase the rate at which the crystals dissolved. The mixture changed to a deeper golden orange color upon completion of stirring. This solution was heated to increase solvation. The solution was then poured through vacuum filtration. The filtration process was accomplished to remove any impurities from the liquid. The remaining liquid was transferred to an ice bath to speed up the crystallization process. As a result of rapid cooling, powdered crystals formed at the base of the reaction tube. Upon attempted recovery through vacuumed filtration, the majority of crystals escaped due to size. A limited amount, however, was gathered from the filter paper to test its melting point. The remaining solution was then reheated for a second attempt at crystallization. Repeated appearance of powdered crystals led to preserving the solution for crystallization at a later date. In determining the melting point of the crystals recovered, onset occurred at 170.0 degrees Celsius and clear point was reached at 174.9 degrees Celsius.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">90% EtOH 10% Water ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Purification Solution ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Amount Solvent || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">0.182g Aldol Reaction Product ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Amount Solution || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">100 drops


 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Melting Point ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Onset Point || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">170.0 degrees Celcius ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Melting Point || <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">174.9 degrees Celcius ||

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Analysis:

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Part 1:

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Solubility test performed on Resorcinol, Anthracene, and Benzoic acid with solvents Water, Toluene, and Ligroin exemplified the defined chemical principle that “like dissolves like”. Resorcinol has two polar hydroxide groups attached to parent chain of cyclohexane <span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;"> it's a benzene ring, rather than cyclohexane <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">. Each OH group attached to the molecule can dissolve approximately three or four carbons adjacent to that group from the ring <span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;"> what? please explain further <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">. When introduced to the hydroxlic solvent of water at room temperature, solubility occurred instantaneously as the test tube became cold to the touch. Anthracene was partially miscible in Ligroin and Toluene because of the hydrocarbon structure of both solute and solvent. It lacked any solubility with water at room temperature because this compound is non-polar. Benzoic acid was partially soluble in water and Ligroin, and completely soluble in Toulene because this particular solute is chemically arranged with one polar hydroxide and an additional oxygen molecule attached to a hydrocarbon chain.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Selection of an ideal crystallization solvent is one that will dissolve the solute as heat is introduced and not when mixed at room temperature. For example with the addition of heat on intermolecular forces, the structure of Benzoic acid degraded and solubility increased. All three solutes displayed partial solvation interactions when heat was applied to Ligroin. Variability of crystallization presented as flat or needles upon cooling to room temperature. Of the three solutes, Resorcinol and Anthracene only displayed partial solubility with the addition of heat to the Toulene solution. Benzoic acid was not applicable in Toulene because it completely dissolved at room temperature.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Part 2:

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">To reproduce the process of dissolving the solute accurately, the mathematical calculation derived from the proportion written in The Handbook of Chemistry and Physics provided an established limit for the measurements taken. It was determined that at ninety nine degrees the solution would dissolve the measured 0.060 g of Phthalic acid per 0.333mL of water. The substance totally dissolved with the addition of 0.25mL during experimentation. To successfully perform the experiment under the limit set by calculations, lessened the potential for excessive impurity additions.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Careful technique of alternate heating and cooling the test tube ensured a limited amount of impurities added when reaching total solubility at 0.25mL. Upon reaching this dissolved level, cooling crystallization at room temperature became more evident at the base of the tube. Because of complete saturation of solute in 0.25ml, maximum recovery was expected. Further addition of liquid would lower the potential for recovery as a result of an excessive amount of solvent. Percent recovery for crystallization of phthalic acid was 71.7%.. High recovery occurred because of the highly saturated solvation allowing a majority of the pure compound to precipitate out in the solution.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Part 3:

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Decolorizing organic compounds is not always a required technique but can be carried out by boiling a substance with charcoal. Its large surface area allows for many molecules to bind to it, thus making charcoal an effective agent. Decolorization of brown sugar might not have succeeded during experimentation because too little charcoal was mixed. If a limited amount of charcoal is added to the solution during the decolorization process, then the substance will retain its color after filtration. On the contrary, adding an excessive amount of charcoal will remove some of the product along with impurities. Through analysis of both experiments conducted, data suggests adding charcoal in staggered portions until decolorization is reached might be a more effective method than simply adding fixed amounts. Gradual addition of charcoal may also reduce the potential for error and eliminate repeated trials.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Part 4:

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">During purification of the Adol product, solvent was added in small increments until there was no observed change in the solid impurities. The solution gained a dark red orange color as a result of the dissolved solute. As more solvent was added, the solution appeared lighter orange in color. This indicated a completely dissolved Aldol product with only impure solids remaining in the test tube. Rapid cooling of the solution and high concentration of dissolved Aldol product led to minimal precipitate in the first crystallization attempt. Through observation of a noticeable amount of settled fine crystals, it was hypothesized that the process of vacuum filtration would retain the crystals. After initiating the vacuum filtration apparatus, the small radii of crystals were lost through the porosity of the filter paper. A small amount of crystal residue was recovered from the paper for melting point comparison. Since the compound was still suspended in solution, the solvation <span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">solution? <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;"> was reheated for a second attempt at crystallization. In theory, the substance should have precipitated out of suspension with the longer cooling time at room temperature. However, the solution became clouded with no crystallization. This outcome could have occurred because of the amount of pure substance in the solvation. Since the saturation level was so high in the solution, it possibly could have not held the pure compound long enough for the crystals to slowly form. The cloudiness could have formed as a result of the solution reaching a rapid equilibrium without a pure compound dissolved.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Since the reaction tube was saved, further attempts at crystallization will be conducted by adding twenty percent more of the solvent to the reaction tube. Once heated a slow cooling will allow for a more evident crystallization process. If this trial is unsuccessful, then a final experiment will involve placing the reaction tube in a centrifuge for separation of crystals.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">With a melting point range of 4.9 degrees, the recovered range was much sharper than the 44.2 degree melting point range of the impure Aldol product. This resulted in a purer recovery of the aldol product. Successful crystallization of any compound is a challenging task, however it is a crucial skill in an organic chemistry lab.


 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Post Lab Question: **

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">A. Calculating the percent recovery is the process of obtaining a pure substance from an impure compound. Recovery can be calculated through the equation; Recovery = mass of purified substance / mass of the impure substance. A recovery yielding 100% is considered to be ideal.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Ty Trate started out with 1.106 grams of a product and recovered 0.884 grams after the recrystallization process. By inserting these values into the equation, Ty Trate receives a 79.9% yield.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">Percent Recovery = 0.884 grams / 1.106 grams x 100 = 79.9%

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 14px;">B. With the information given, it appears that Ty succeeded in purifying his product during the recrystallization process. Since the melting point of the impure substance was recorded at 131.6-144.3 degrees C, and the observed melting point of the recovered substance was recorded at 143.7-144.9 degrees C, it is obvious that the recovered substance has an average melting point of 6.35 degrees C greater then that of the initial substances average melting point. This melting point difference indicates that the recovered substance is more pure than the initial substance. When impurities are included in an otherwise pure substance, those impurities prevent the chemical bonds from the pure substance from forming a crystal lattice. This lattice contributes to then strength of the bond, correlating to an increased melting point. <span style="color: #800000; font-family: Arial,Helvetica,sans-serif; font-size: 14px;">good answer.