Organic



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    ANS BC



  • @You-Knowwhere The crux of the question is the application of identification tests predominantly meant for alcohols after converting the alkyl halides into their corresponding alcohols

    LUCAS TEST
    a test in alcohols that is conducted to test and differentiate between the types of primary, secondary or tertiary alcohol. It uses the differences in reactivity of hydrogen halides and the three classes or types of alcohol. In the reaction the hydrxy 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 generally implies that no reaction will occur, secondary alcohols result in the solution turning cloudy after a period of three to five minutes and if the solution immediately turns cloudy it signifies that the alcohol present is tertiary, benzyl alcohol or allyl alcohol. This particular sort of test is generally conducted at room temperature.

    Victor Meyer Test
    This test consists of the following steps

    i) The given alcohol is first converted into its alkyl iodide by treating it with P&Iodine.

    ii) The alkyl iodide is then treated with silver nitrite (AgNO2) to convert it into corresponding nitro alkane.

    iii)The nitroalkane is then treated with nitrous acid (HNO2), i.e., NaNO2 + HCl.

    iv)The resulting solution is finally made alkaline with aqueous NaOH or KOH.

    If blood red colouration appears it is a primary alcohol.

    If blue colouration appears it is a secondary alcohol.

    If the solution remains colourless, itindicates a tertiary alcohol.

    RCH2OH + P/I2 --->RCH2-I +AGNO2 ---->RCH2NO2 +HONO --->RC(=NOH)-NO2 +NaOH--->Blood red colour

    R2CH-OH +P/I2 -->R2CH-I +AgNO2 --->R2CHNO2 + HONO --> R2C(N=O)-NO2 + NaOH-->Blue colour

    R3C-OH + P/I2 -->R3C-I +AgNO2 -->R3C-NO2 +HONO-->NO REACTION + NaOH --> Colourless

    HALOFORM TEST
    This test does not distinguish 1°, 2°, 3°
    alcohol but is specific for only one class of alcohol. This is the secondary methyl alcohol. If the alcohol
    contains a methyl group attached to a carbon that also has a hydrogen and an OH group then it will give a
    positive iodoform test. The formation of a yellow precipitate indicates a positive test.

    To summarise

    By oxidation: Primary alcohol will give carboxylic acid which on reaction with ethanol give a fruity smell. Secondary alcohol will give ketone which can be detected by iodoform test. Tertiary alcohol won't oxidize (if the temperature is not high).
    Lucas test can also distinguish them depending on the turbidity of the solution. Primary alcohol - no turbidity. Secondary alcohol - turbidity after 5 minutes. Tertiary alcohol - instant turbidity.
    Victor Mayer's test can also distinguish them.
    Primary alcohol - final colour red.
    Secondary alcohol - final colour blue.
    Tertiary alcohol - no colour change.


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