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level: level 3

Questions and Answers List

level questions: level 3

QuestionAnswer
amines salts solubilitythey are soluble in water and insoluble in organic solvents live ethers
explain the basic nature of amines by pKb or Kb valuespKb value of ammonia is 4.75 aliphatic amines pKb values lie in the range of 3 to 4.22
why are aliphatic amines stronger bases than ammoniadue to +I effect of alkyl groups leading to high electron density on the nitrogen atom
why then are aromatic amines weaker than ammoniadue to electron withdrawing nature of aryl group
what does basic character of amines depend onit depends on the ease of formation of the cation by accepting a proton from the acid. the more stable the cation is relative to the amine more basic is the amine
relation of alkyl group with amines and basicitythe alkyl group causes an +I effect and hence nitrogen readily loses electrons. also due to dispersal of +ve charge due to +I effect
order of basicity of amines in the gaseous statetertiary amines >secondary amines>primary amines>NH3
what happens to the basicity of amines in aqueous statethe +ve charge not only gets stabalised by +I effect but also due to solvation of water molecules. hence the greater the size of the ion the less will be the solvation.
order of basicity in aq. mediumprimary>secondary>tertiary
which structure has only two resonating structure in arylaminesanilinium
how is the basic strength of aniline increasedit is increased by stubstituting electron releasing groups like -OCH3,-CH3
acylationaliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and ethers by nucleophilicsubstitution reaction
how does the reaction acylation shift the equilibrium to the right hand sidethis reaction is carried out in the presence of a base stronger thanamine like pyridine which removes the HCl so formed
reaction of amines with benzoyl chloridebenzoylation
carbylamine reactionsprimary amines on heating with chloroform(CHCl3) and ethanolic potassium hydroxide form isocyanides or carbylamines which are foul smelling.
what is special about carbylamine reactionused to test for primary amines does not show reaction with secondary or tertiary amines
reaction with nitrous acidthree classes of amines react differently with nitrous acid which is prepared in situ from a mineral acid and sodium nitrite
primary aliphatic amines react with nitrous acid to formaliphatic diazonium salts which being unstable liberate N2 gas
aromatic amines react with nitrous acid at low temp. to formdiazonium salts in presence of NaNO2+HCl
reaction with arylsulphonyl chloridehisenberg's reagent reacts with primary and secondary amines to form sulphonamides
what is hinsberg's reagentC6H5SO2Cl