Lucas test reagent

The test requires that the alcohol initially be soluble in the Lucas test reagent solution. As the reaction proceeds, the corresponding alkyl chloride is formed, which is insoluble in the reaction mixture. As a result, the solution becomes cloudy. In some cases a separate layer may be observed. 

The difference in reactivity of three classes of alcohols with HCl distinguishes them from one another (Lucas test). Acohols are soluble in Lucas reagent (cone. HCl and ZnCla) while their halides are immiscible and produce turbidity in solution. In case of tertiary alcohols, turbidity is produced immediately as they form the halides easily. Primary alcohols do not produce turbidity at room temperature. 

A common analytic test used to classify alcohols is the Lucas test. This test is for alcohols with six or fewer carbon atoms (and therefore soluble in reagent mixture). They react with HCl/ZnCl2 to form an alkyl chloride, which is insoluble in the reaction mixture (causing the solution to turn cloudy). The time required for the reaction to occur indicates the type of alcohol. Table 3-1 summarizes the time required for each type of alcohol. 

Locating an organic compound, 1128 Lubrication of ground glass joints, 225 Lucas test, 261 reagent, 261 ... 

The Lucas Test The Lucas reagent reacts with primary, secondary, and tertiary alcohols at predictable rates, and these rates can distinguish among the three types of alcohols. When the reagent is first added to the alcohol, the mixture forms a single homogeneous phase The concentrated HC1 solution is very polar, and the polar alcohol-zinc chloride complex dissolves. Once the alcohol has reacted to form the alkyl halide, the relatively nonpolar halide separates into a second phase. (R—OH dissolves, but R—Cl does not.)... 

The Lucas test involves adding the Lucas reagent to an unknown alcohol and watching for the second phase to separate (see Table 11-2). Tertiary alcohols react and show a second phase almost instantly because they form relatively stable tertiary carbocations. Secondary alcohols react in about 1 to 5 minutes because their secondary carbocations are less stable than tertiary ones. Primary alcohols react very slowly. Since the activated primary alcohol cannot form a carbocation, it simply remains in solution until it is attacked by the chloride ion. With a primary alcohol, the reaction may take from 10 minutes to several days. 

In the Lucas test, the Lucas reagent reacts with 1°, 2°, and 3° alcohols. The alcohols are distinguished by their reactivity with the Lucas reagent 33 alcohols react immediately 2C alcohols react within 5 minutes and 1 alcohols react poorly at room temperature. Because the compound reacts with the Lucas reagent in 4 minutes, then the structure of C4H10O, a 2° alcohol, is sec-butyl alcohol ... 

Whether an alcohol is primary, secondary, or tertiary is shown by the Lucas test, which is based upon the difference in reactivity of the three classes toward hydrogen halides (Sec. 16.4). Alcohols (of not more than six carbons) are soluble in the Lucas reagent, a mixture of concentrated hydrochloric acid and zinc chloride. (Why are they more soluble in this than in water ) The corresponding alkyl chlorides are insoluble. Formation of a chloride from an alcohol is indicated by the cloudiness that appears when the chloride separates from the solution hence, the time required for cloudiness to appear is a measure of the reactivity of the alcohol. 

Whether an alcohol is primary, secondary, or tertiary can be determined by taking advantage of the relative rates at which the three classes of alcohols react with HCl/ZnCl2. This is known as the Lucas test. The alcohol is added to a mixture of HCl and ZnCL—the Lucas reagent. Low-molecular-weight alcohols are soluble in the Lucas reagent, but the alkyl halide products are not, so the solution... 

Many chromium(VI) compounds are suspected carcinogens. K you would like to run this test, talk to your instructor first. The Lucas test will distinguish between 1°, 2°, and 3° alcohols, and you should do that test first. If you run the chromic acid test, be sure to wear gloves to avoid contact with this reagent. 

Although primary alcohols are first oxidized to aldehydes, the aldehydes are further oxidized to carboxylic acids. The ability of chromic acid to oxidize aldehydes but not ketones is taken advantage of in a test that uses chromic acid to distinguish between aldehydes and ketones (see Experiment 52D). Secondary alcohols are oxidized to ketones, but no further. Tertiary alcohols are not oxidized at all by the reagent hence, this test can be used to distinguish primary and secondary alcohols from tertiary alcohols. Unlike the Lucas test, this test can be used with all alcohols regardless of molecular weight and solubility. 

Chemical Tests. The ignition test should indicate that this compound is an aliphatic species. Does your result confirm this fact Perform the ceric nitrate test to demonstrate the presence of the —OH group and the Lucas test to demonstrate that a secondary alcohol has been prepared. If you were required to prepare a solid derivative of this alcohol, which one would you select It may be of interest to determine the solubility of this product in water, ether, concentrated sulfuric, and 85% phosphoric acids. Do your results agree with what you would predict What test(s) would you perform to establish that one of the starting reagents was an aldehyde ... 

In a 10 X 75-mm test tube, or in a small tube prepared from a Fhsteur pipet (see Lucas test), place 2 drops of a liquid unknown (—15 mg if a solid) followed by 0.5 mL of methylene chloride. Add dropwise, in the hood with shaking, a 2% solution of bromine in methylene chloride solvent. The presence of an unsaturated hydrocarbon will require 2-3 drops of the reagent before the reddish-brown color of bromine persists in the solution. 

An unknown organic liquid, compound A, was found to bum with a yellow, sooty flame and give a positive Lucas test ( 5 min). Upon treatment with sodium dichromate-sulfuric acid solution it produced compound B, which also burned with a yellow, sooty flame. Compound B gave a positive 2,4-dinitrophenylhydrazine test, but a negative result when treated with the Tollens reagent. However, compound B did give a positive iodoform test. 

To 1 ml. of the alcohol in a small test-tube, add quickly 6 ml. of Lucas reagent at 26-27°, close the tube with a cork, shake, and allow to stand. Observe the mixture during 5 minutes. The following results may be obtained —... 

A test used to determine whether an alcohol is primary, secondary, or tertiary. The test measures the rate of reaction with the Lucas reagent, ZnCl2 in concentrated HC1. Tertiary alcohols react fast (seconds), secondary alcohols react more slowly (minutes), and primary alcohols react very slowly (hours), (p. 481)... 

Refer to the isomeric pentyl alcohols of Problem 1(a), p. 515. (a) Indicate which (if any) will give a positive iodoform test, (b) Describe how each will respond to the Lucas reagent, (c) Describe how each will respond to chromic anhydride, (d) Outline all steps in a possible synthesis of each, starting from alcohols of four carbons or less, and using any necessary inorganic reagents. 

Alcohols are neutral compounds. The only other classes of neutral compounds used in this experiment are the aldehydes, ketones, and esters. Alcohols and esters usually do not give a positive 2,4-dinitrophenylhydrazine test aldehydes and ketones do. Esters do not react with Ce(lV) or acetyl chloride or with Lucas reagent, as alcohols do, and they... 

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