Group No. 7 Chemistry Laboratory 204 A Members: 1.Abdulwahid, 1.Abdulwahid, Sheena-Joy M. 2. Lintag, Patrick Amos D.A. 3. Muham, Pearlmaida A.
Date Performed Date Submitted Instructors Initials
Laboratory Report Sheet
Alcohols
:Dec 14, 2011 :Jan 08, 2012 :
Activity
6
Objectives:
1. Distinguish primary and secondary from tertiary alcohols through Chromic acid test. 2. Distinguish tertiary and secondary from primary alcohols through Lucas test. 3. Explain the formation of esters and describe its odor. 4. Explain the reaction in special test for methyl alcohol. 5. Differentiate and explain the reaction of Iodoform test in ethyl alcohol, isopropyl alcohol and methyl alcohol. 6. Explain the reaction and result in Acrolein test.
Data
Interpretation:
Name of Test/ Test Compounds I. Chromic Acid Test ethyl alcohol
Reagents
Results
K 2Cr2O7 Color changed from orange to green within 45sec.
n-butyl alcohol Color changed from orange to green within 45 sec. sec-butyl alcohol Color changed from orange to green within 1min and 24 sec. tert-butyl alcohol No reaction
II. Lucas Test
Lucas Reagent
tert-butyl alcohol
Formed precipitate immediately
sec-butyl alcohol
Formed precipitate within 3mins and 17sec
n-butyl alcohol
No reaction
benzyl alcohol
Formed precipitate within 30 sec
III. Esterification
CH3COOH
ethyl alcohol
A pleasant (cherry-like) odor was formed within 1min.
tert-butyl alcohol A pleasant (mint) odor was formed within 1min.
IV. Special Test for
C6H4(OH)2
Formed a yellow precipitate
methyl alcohol
V. Iodoform Test
iodine
ethyl alcohol
Yellow precipitate with a pungent smell
isopropyl alcohol
Yellow precipitate with a pungent smell
methyl alcohol
VI. Acrolein Test Glycerol
No reaction
C3H8O3
Pungent smell
Chromic acid (acidified dichromate, an oxidizing agent) can also be used to distinguish primary alcohols and secondary alcohols from tertiary alcohols by oxidizing the alcohol. Primary alcohols (n-butyl alcohol and ethyl alcohol) are oxidized to aldehyde; secondary alcohols (sec-butyl alcohol) are oxidized to ketones; and tertiary alcohols (tert-butyl alcohol) are not oxidized. During the oxidation, the orange-red color of the chromic acid changes to a blue-green solution. Tertiary alcohols did not oxidize due to the absence of the alpha hydrogen which is present in primary alcohols and secondary alcohols. During the oxidation, the hydrogen of the OH group and the hydrogen from the carbon atom attached to the OH. Ethyl alcohol and n-butyl alcohol are the fastest to oxidize with 45 sec, secondary with 1min and 24 sec. This is because of the Sn1 mechanism where a substitution reaction favors on less crowded molecules. The chemical equations for the oxidation of primary and secondary alcohols are as follows: Primary:
Secondary:
The Lucas test is a test in alcohols that is conducted to distinguish tertiary alcohols and secondary alcohols from primary alcohols. It uses the differences in r eactivity of hydrogen halides and the three classes or types of alcohol. In the r eaction the hydroxyl group is replaced by chlorine. The time it takes in the appearance of turbidity is used as a measure for determining the class of alcohol. A primary alcohol (n-butyl alcohol) generally implies that no reaction will occur, secondary alcohols( sec-butyl alcohol) r esult in the solution turning cloudy after a period of 3mins and 17seconds and if the solution immediately turns cloudy it signifies that the alcohol present is tertiar y(tert-butyl alcohol), benzyl alcohol or alkyl alcohol. This particular sort of test is generally conducted at room temperature. The chemical equations are as follows: Tertiary:
Secondary: Esterification is the process of producing esters. It is formed when carboxylic acid where in this activity the acetic acid are heated with alcohols (tert-butyl alcohol and ethyl alcohol) in the presence of an acid catalyst which is usually the concentrated sulfuric acid. Esters have generally pleasant odors. In the activity when the ethyl alcohol was heated with the acetic acid, formed a pleasant (cherry-like) odor. Tert-butyl alcohol
when heated with the acetic acid also formed a pleasant (mint) odor. The chemical equation of this reactions are as follows:
Special Test for Methyl Alcohols is a test conducted to test the properties of methyl alcohols. By heating the copper on the Bunsen flame and dipping into the methyl alcohol-water mixture shows that methyl alcohols are flammable. And it is insoluble in resorcinol so it produced a yellow precipitate. Iodoform Test is a test for methyl carbonyl (secondary alcohol with adjacent methyl group) and methyl carbonyl groups. Reagents include 10% KI and NaClO. Positive result is exhibited by the formation of yellow crystals or precipitate. Co mp ou nd s wi th a methyl group next to a carbonyl group give a positive result with the iodoform (tri-iodomethane) test. Ethanol and secondary alcohols with a methyl group attached to the same carbon as the OH group will also give a positive iodoform test. This is because the iodine oxidizes the alcohols to a carbonyl compound with a methyl group next to the carbonyl group. When a methyl carbonyl compounds react with iodine in the presence of a base,the hydrogen atoms on the carbon adjacent to the ca r bo ny l gr o u p ( a hy dr o g en s ) ar e subsituted by iodine to form triiodomethyl carbonyl compounds which react with OH to produce iodoform and carboxylic acid. Chemical reaction:
Acrolein test is the test conducted for the presence of glycerin. When glycerol is heated with KHSO4 a very offensive smell is produced due to formation of acrolein. Acrolein is the simplest unsaturated aldehyde that has a disagreeable smell. When glycerol is heated, it decomposes into acrolein. Acrolein is produced by the reaction of potassium bisulfate on glycerol. O
CH2OH
+
HOHC CH2 OH glycerol 1,2,3 - propanetriol
H
KHSO4
+
H2O
(
CH2 acrolein or propenal with pungent odor
Answers to Questions : 1. Compare the relative ease of oxidation of primary, secondary and tertiary butyl alcohol toward acid dichromate based on the time required for the solution to change color.
Answer: Primary alcohols react the fastest, with secondary alcohols next and tertiary alcohols not reacting at all. This is because the mechanism of this reaction is Sn1 which is a substitution reaction that favors attack on less crowded molecules.
2. What is the significance of the Lucas test? Answer: The significance of Lucas test is, it is the continuation of the test for distinguishing alcohols. Since chromic acid test is to distinguish primary alcohols and secondary alcohols from tertiary alcohols, Lucas test is to distinguish tertiary alcohols and secondary alcohols from primary alcohols. Thus, we will be able to differentiate all the classification of alcohols. 3. Distinguish ethyl alcohol from methyl alcohol. Answer: Methanol and ethanol are different chemicals. Methanol has a very sharp scent compared with , Ethanol. Methanol and ethanol also have different flame colors when burned. Methanol produced light green flame while ethanol produces blue, orange, and green flame. Methanol when burned to form a light green comes from the hydrolysis process will form the alkyl compounds called borax, and Borax is also quicker to react with Methanol. Ethanol requires a catalyst when it is burned. 4. What is responsible for the characteristic odor of the acrolein test? Answer: Reaction of potassium bisulfate and glycerol will form acrolein which has a pungent smell. This will happen when glycerol is heated and decomposes into acrolein. 5. Give one important commercial method of preparing ethyl alcohol in the country. Write the chemical reaction involved.
Answer: Making wine from grapes is a typical commercial country side activity [Sugar] C6H12O6 ²² 2 C2H5OH + 2 CO 2
Conclusion:
Alcohols are compounds with hydroxyl group attached to one carbon atom. There are 3 classification of alcohols, it includes primary alcohols, secondary alcohols and tertiary alcohols. These alcohols can be distinguished from one another through chromic acid test ( distinguish primary alcohols and secondary alcohols from tertiary alcohols) and the lucas test ( distinguish tertiary alcohols and secondary alcohols from primary alcohols). In the chromic acid test, tertiary alcohols will not react due to the absence of alpha hydrogen while primary alcohols are oxidize to aldehydes and secondary alcohols oxidize to ketones due to the presence of alpha hydrogen. In lucas test primary alcohols will not react while tertiary alcohols will immediately form a precipitate and s econdary alcohols will form precipitate between 3-5mins. Esterification is the process of producing esters by reacting the carboxylic acid with organic acids. Esters have generally pleasant unique odors. Special test for methyl alcohol is conducted to test the properties of methyl alcohol where it will
burn in a nonluminous flame and it is completely miscible with water and other organic solvents. Iodoform Test is a test for methyl carbonyl (secondary alcohol with adjacent methyl group) and methyl carbonyl groups. Positive result is exhibited by the formation of yellow crystals or precipitate. And lastly, acrolein test is to test for the presence of glycerine. Wherein when glycerol is heated it decomposes to acrolein which has a pungent smell.
http://chemicalland21.com/petrochemical/n-butanol.htm http://chemicalland21.com/industrialchem/solalc/benzyl%20alcohol.htm http://www.harpercollege.edu/tm-ps/chm/100/dgodambe/thedisk/qual/chromic.htm http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/alcohol1.htm
http://www.chemistry.ccsu.edu/glagovich/teaching/316/qualanal/tests/iodoform.html
