NEET Chemistry Questions: differentiation & conversion - organic chemistry

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A compound A of formula C3H6Cl2 on reaction with alkali can give B of formula C3H6O or C of formula C3H4. B on oxidation gave a compound of the formula C3H6O. C with dilute H2SO4 containing Hg2+ ion gave D of formula C3H6O, which with bromine and NaOH gave the sodium salt of C2H4O2. Then A is :





No explanation available.

Identify the product (A) in following reaction series, CH3CNNa/C2H5OH(X)HNO2(Y)O(Z)Tollens reagent(A) :





(c) CH3CNNa/C2H5OHCH3CH2NH2HNO2CH3CH2OHOCH3CHOTollens reagentCH3COOH

Vapour density of an organic compound is 23.0. It contains 52.17% of carbon and 13% of hydrogen. The compound gives iodoform test. The compound is:





(a) Molar mass of compound  is 46 which is of ethanol. It also gives iodoform test.                               

An amine is reacted with benzene sulphonyl chloride then a solid compound is formed which is insoluble in alkali. The amine is:





(b) Secondary amine is reacted with benzene sulphonyl chloride to form solid compound which is insoluble in alkali

An organic compound X on treatment with acidified K2Cr2O, gives compound Y which reacts with I2, and NaOH to form CHI3. The compound X can be





 

its 2 degree alcohol, which on oxidation gives ketone, and since product will be propanone , so it will give +ve iodoform reaction.

Give test to differentiate 1,1-dichloroethane and 1, 2-dichloroethane:





To differentiate between 1,1-dichloroethane and 1,2-dichloroethane, the test involves first treating with aqueous KOH and then with 2,4-dinitrophenylhydrazine (2,4-DNP). 1,2-dichloroethane will give a positive test (orange precipitate) while 1,1-dichloroethane will not react.

The reagent used in dehydrohalogenation process is:





Dehydrohalogenation is the process of eliminating hydrogen and halogen atoms from an alkyl halide to form an alkene. The reagents commonly used for this process are alcoholic KOH, sodium amide (NaNH2), and sodium ethoxide (C2H5ONa). Therefore, the correct option is 'all of these'.

The reaction, CH2=CHCHOHXgives:





The given reaction is an example of addition of hydrogen halide (HX) to an alkene (ethene). According to Markovnikov's rule, the hydrogen atom gets added to the carbon with fewer hydrogen atoms, and the halide (X) gets added to the carbon with more hydrogen atoms. Hence, the product is CH2=CHCHO.

The reagent used in dehalogenation process is:





Zn dust is used for dehalogenation,

CH2X·CH2Xalc.Zn dustCH2=CH2

Zn-Cu couple used as reducing agent is:





 

Zinc-copper couple, which can be used as a reducing agent, is obtained by coating zinc with copper. Zinc is dipped in a solution of copper salt. It displaces copper and copper gets deposited over the surface of  granulated zinc.

Which reaction sequence would be best to prepare 3-chloro-aniline from benzene?





To prepare 3-chloroaniline from benzene, the best sequence is: nitration (to introduce -NO2 group), chlorination (to introduce -Cl group at 3-position), and finally reduction (to convert -NO2 to -NH2). Nitration is carried out first as the nitro group is a strong deactivating group.

An unknown compound A has a molecular formula C4H6. When A is treated with excess of Br2 a new substance B with formula C4H6Br4 is formed. A forms a white ppt. with ammoniacal silver nitrate solution. A may be:





(a) A white precipitate with am. AgNO3 confirms the presence of terminal alkyne.

The reduction of an alkyne to alkene using Lindlar's catalyst results into:





Lindlar's catalyst (Pd-CaCO3 poisoned with Pb(OAc)2 and quinoline) is used for the semi-hydrogenation of alkynes to cis-alkenes. It adds hydrogen atoms in a cis fashion across the triple bond, selectively producing the cis-alkene product.

Acetylene can be converted to higher alkyne using the following sequence of reactions:





(c)CHCH+NaCHCNaRXCHCR      CHCH+RMgXCHCMgXRXCHCR

RCOOHRCH2OH. This mode of reduction can be effected only by:





(d) Na/C2H5OH, LiAlH4 or NaBH4 are used for this purpose.