Names: Anasario, Jc BelleDate Performed: April 30, 2015

Names: Anasario, Jc BelleDate Performed: April 30, 2015

Jubelag, CarmelliDate Submitted: May 7, 2015

Labatos, Marie Isabella

Experiment 9

Acyl Compounds: Soaps and Detergents

I. Introduction

Acyl is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid and usually derived from a carboxylic acid. Carboxylic acid derivatives are a group of compounds which also contain a carbonyl group. The difference of carboxylic acid to its derivatives is that they have an electronegative atom: oxygen, nitrogen, or a halogen, attached to the carbonyl carbon. Acyls are given with the formula RCO-, where R represents an alkyl group that is attached to the CO group with a single bond and has the acyl group:

Acyl groups can in principle be derived from other types of acids such as sulfonic acids, phosphonic acids. They are usually attached to a larger molecular fragment, in which case the carbon and oxygen atoms are linked by a double bond. The reaction involved in the conversion of carboxylic acid to its derivatives and vice versa is called the neucleophilic acyl substitution wherein the Cl, OCOR, OR, or NR2 group bonded to C=O acts as the leaving group. The protonation of the C=O bond in a carboxylic acid or derivative converts it into a stronger electrophile, which reacts more rapidly with nucleophiles.

This experiment also involves the process of saponification where triacylglycerols undergo reactions the same of that of the low molecular mass esters. This is a process of producing soap or convert a fat into soap especially by reaction with an alkali. In the production of natural soap, sodium or potassium salts of fatty acids made by boiling lard or other animal fat together with lye and potash are the primarily surfactants which can be produced easily from petrochemicals. Hydrolysis also takes part in a basic medium which results into long-chain carboxylate salts and glycerol. It also leads to the production of glycerol and crude soap.

This experiment aims to observe and compare the general properties as well as the acidity of carboxylic acids and phenols. It also aims verify experimentally the interconversion among acyl compounds. Also, it aims to give proper knowledge on how to prepare soap and to compare its properties with the synthetic detergents.

II. Data and Results

A. Solubility and Acidity of Carboxylic Acids

1. Water Solubility

Acetic Acid

Benzoic Acid

Sodium Benzoate

Soluble

Insoluble

Soluble

Rxn of the Blue Litmus Paper

Turned to Red

Turned to Red

Remained blue

2. Relative Acidities of Carboxylic Acids and Phenols

Benzoic Acid

Phenol

Using 10 % NaHCO3

Clear liquid with very small precipitate

Clear peach-colored liquid

Using 10% NaOH

Clear liquid

Clear liquid with peach-colored liquid

B. Hydrolysis of Acyl Compounds

Acetyl Chloride

Acetic Anhydride

Benzamide

Observation

(After heating)

Cloudy solution with tiny bubbles

Clear solution with no bubbles

Clear solution with tiny bubbles

Rxn of the Blue Litmus Paper

Turned to red

Turned to red

Remained blue

B. Saponification of Coconut Oil

(Figure 1. Mixture of ethanol, NaOH, coconut oil and boiling chips) (Figure 2. After washing the soap twice with 15-mL ice-cold distilled water)

C. Comparison of Soaps and Detergents

Soap Sample

Reaction with Hard Water

Reaction with Soft Water

Emulsifying Action

Blank

Scum formation

Opaque liquid

Cloudy solution with formation of bubbles on top layer

Clear liquid

Soap Sample

Hydrolysis

Reaction with Acid

Litmus paper

Blue-blue; red - red

Cloudy solution

Detergent Sample

Hydrolysis

Reaction with Acid

Reaction with Hard Water

Litmus Paper:

Blue to Blue

Red to Blue

Clear liquid

Cloudy liquid

Detergent Sample

Reaction with Soft Water

Emulsifying Action

Blank (Emulsifying Action)

Opaque

Cloudy solution with bubbles on top layer

Clear liquid

III. Discussion

Table 1 shows the water solubility of acetic acid, benzoic acid, and sodium benzoate. In the litmus paper test, acetic acid and benzoic acid turned the blue litmus paper into red which means that the solutions are acidic. The hydrogen atom in the carboxyl group (COOH) in carboxylic acids such as acetic acid and benzoic acid can be given off as an H+ ion (proton), giving them their acidic character. On the other hand, the blue litmus paper remained blue by testing sodium benzoate. Acetic acid and sodium benzoate were soluble in water while the benzoic acid is insoluble in water. Since liquid acetic acid is a hydrophilic polar protic solvent, it can dissolve polar compounds and non-polar compounds, that is why it readily mixes with water. The same is true with sodium benzoate.

Table 2 shows the relative acidities of benzoic acid and phenol. The reaction of benzoic acid with 10% NaOH and 10% NaHCO3 shows that it is acidic. The reaction of phenol shows that it is weakly acidic. Sodium hydroxide (strong base) converts benzoic acid (weak acid) into sodium benzoate (salt). Through this we converted an acid that is insoluble in water into a salt that is soluble in water. The conjugate base of a weak acid is an anion that is soluble in water. In the case of phenols, they are weak acids that are insoluble in water. Strong bases convert phenols into water soluble salts. Carboxylic acids react with sodium bicarbonate much as they do with sodium hydroxide. The difference is that carbon dioxide and water are byproducts of the reaction with bicarbonate. Carbonic acid decomposes as it forms into carbon dioxide and water. The carbon dioxide is visible as bubbles. Thus, sodium bicarbonate is used to determine the presence of a carboxylic acid by the evolution of bubbles. The bicarbonate ion converts the benzoic acid into its conjugate base, the benzoate. The phenol, however, does not react with the bicarbonate making it insoluble.

In Table 3 the acetyl chloride and acetic anhydride turned the blue litmus paper into red. The benzamide had still a blue litmus paper. The acetyl chloride sample formed a cloudy solution accompanied by a gas before heating and a slightly cloudy sample after heating. Acetic anhydride and benzamide have clear samples before and after heating. The gathered data showed that acetic anhydride and benzamide are less reactive than the acetyl chloride which produced a cloudy liquid with gas vapors. This is because hydrolysis reactions are done to differentiate the samples based on the fact that more reactive compounds are readily hydrolyzed by water.

Hydrolysis of soaps and detergents are tested using blue and red litmus papers. The blue litmus paper remained blue in both soap and detergent. The red litmus paper turned blue only for the detergent sample but remained red for the soap sample. Therefore, the detergent is basic and soap produced was a mixture of carboxylate salts. The addition of the polar solvent water formed clusters of molecules known as micelles where in the polar ends are on the outside of the cluster and the non-polar ends are in the middle.

The reaction of an acid with soap and detergent is also shown. The soap gives a cloudy solution while the detergent had a clear liquid. These results could help us determine the difference in the basicity of the two samples. Since the detergent is more neutralized in the acid, it is more basic than the soap sample.

The same tables show the reaction of the soap and detergent samples with soft and hard water. The reaction of both the detergent and soap samples with NaCl (soft water) produced a clearer solution than with the CaCl2 (hard water) which gave a more cloudy appearance of the liquid. Because the soft water contains lesser minerals than the hard water, it produced a clearer solution. There is a formation of a scum in the hard water test mainly because of the formation of the grey-white insoluble calcium compound formed by the reaction between the soap and detergent molecules with the calcium.

Emulsifying action of soap and detergent is also shown in the last two tables. The detergent had more bubbles than the soap sample. Also, the detergent produced a more cloudy liquid than the soap solution. Soaps can react with metal ions and may form insoluble precipitates known as soap scum. Detergents work similarly but do not form precipitates with metal ions.

The blank was also observed. There was a formation of two layers, a less dense solution at the top and a clear solution at the bottom having greater amount.

IV. Conclusion

Detergents and soaps are used for cleaning because pure water can't remove oily, organic soiling. Soap cleans by acting as an emulsifier. Basically, soap allows oil and water to mix so that oily grime can be removed during rinsing. Detergents are primarily surfactants, which could be produced easily from petrochemicals. Surfactants lower the surface tension of water, essentially making it 'wetter' so that it is less likely to stick to itself and more likely to interact with oil and grease.

Soap contains the sodium salts of a mixture of long chain carboxylic acids. The acids are less water soluble than the salts and precipitate when soap solution is acidified. Both bases reacted with HCl in a neutralization reaction. Soap is the sodium salt of stearic acid and is soluble in soft water. In practical usage, soap lathers readily with soft water. Soap in hard water is insoluble calcium or magnesium salts which can be seen as white and curdy. Unlike soaps, detergents calcium and magnesium complexes are still hydrophilic. Soaps and detergents are important household material because it is use to remove grease and dirt by emulsifying the grease or bringing it into suspension. Since soap and detergents are molecules which have both properties of non-polar and polar molecules they can act as an emulsifier. An emulsifier is a chemical agent that maintains or create emulsion and capable of dispersing one liquid into another immiscible liquid. This means that while oil, which attracts dirt, doesn't naturally mix with water, soap/detergent can suspend oil/dirt in such a way that it can be removed.

V. References

McMurry, J. and Simanek, E. 2008. Fundamentals of Organic Chemistry. Singapore: Thomson Brooks/Col

Miscrosoft Encarta Inc. Ed. 2009

John W. Hill, Ralph H. Petrucci, General Chemistry, 2nd edition, Prentice Hall, 1999.

(n.d). Retrieved May 6, 2015, from http://www.tutorvista.com/content/chemistry/chemistry-iii/hydrogen/hard-and-soft-water.php