Q25 of 26 Page 1

Write the structures of A, B, C and D in the following reactions:

(a)



(b) Distinguish between the following:


(i) CH3-CO-CH2CH3 and CH3-CH2-CH2-CHO


(ii) Ethanal and Ethanoic acid


(c) Write the structure of 4-Chloropentan-2-one


OR


(a) Write the structures of the main products when Propanal (CH3-CH2-CHO) reacts with the following reagents:


(i) Zn-Hg/ conc. HCl


(ii) H2N-OH/H+


(iii) HCN


(b) Arrange the following in decreasing order of their reactivity towards nucleophilic addition reaction


HCHO, CH3-CO-CH3, CH3-CHO


(c) Give the simplest chemical test to distinguish between the following pairs of compounds:


C6H5CHO and C6H5-CO-CH3


(a)


A – CH3COCl


Acetic acid reacts with phosphorous pentachloride to give Acetyl chloride.


B – CH3CHO


Acetyl chloride undergoes Rosenmund reduction with Pd in the presence of BaSO4 to give Acetaldehyde.


C – CH3CH(OH)CH3


Acetaldehyde reacts with Grignard reagent to give 2-Propanol.


D – CH3CH2OH


Acetaldehyde gets reduced in the presence of Lithium aluminium hydride to give Ethanol.


(b)


(i)


• Butanal is an aldehyde and answers Tollens’ reagent but Ethyl methyl ketone does not answer.


• Upon reaction with Tollens reagent, Butanal gives silver mirror.


(ii)


• Ethanoic acids answers the litmus test by changing red litmus blue whereas Ethanal does not answer this test as it is neutral in nature.


• This test is used for distinguishing Ethanal from Ethanoic acid.


(iii) 4-Chloro-pentan-2-one



OR


(a)


(i) Propanal reacts with Zinc amalgam in the presence of conc. HCl to under goClemmenson Reduction and give the corresponding hydrocarbon, in this case propane.


CH3-CH2-CH3


(ii) Propanal reacts with Hydroxylamine to give the oxime of propane.


CH3-CH2-CH=NOH


(iii) Propanal reacts with HCN to undergo a nucleophilic reaction giving a cyanohydrin.


CH3CH2CH(OH)CN


(b)


• Aldehydes undergo nucleophilic addition reactions more easily than ketones.


• Formaldehyde undergoes nucleophilic addition easily than acetaldehyde.


• Thus, the decreasing order of reactivity is


HCHO>CH3CHO>CH3-CO-CH3


(c)


• Acetophenone reacts with Iodoform test to prove the presence of CH3C=O group.


• This answers by giving a yellow precipitate.


• Benzaldehyde does not answer Iodoform test.


More from this chapter

All 26 →
22

A first order reaction takes 10 minutes for 25% decomposition. Calculate t1/2 for the reaction.

 23

Mr. Roy the principle of one reputed school organized a seminar in which he invited parents and principals to discuss the serious issue of diabetes and depression in students. They resolved this issue by strictly banning junk foods in schools and introducing healthy snacks and drinks like soup, lassi, milk etc. in the school canteens. They also made compulsory half an hour of daily physical activities for the students in the morning assembly. After six months, Mr. Roy conducted a health survey in most of the schools and discovered a tremendous improvement in the health of the students.

After reading the above passage, answer the following questions


(i) What are the values (at least 2) displayed by Mr. Roy?


(ii) As a student, how can you spread awareness about this issue?


(iii) What are tranquilizers? Give an example.


(iv) Why is the use of aspartame limited to cold foods and drinks?


 24

(a) Account for the following:

(i) Eu2+ is a strong reducing agent


(ii) Transition metals are coloured compounds


(iii) Zn has lowest enthalpy of atomization is the 3d series


(b) Complete the following equations:


(i) KMnO4


(ii) Cr2O72- + 14H+ + 6Fe2+


OR


(a) Account for the following


(i) Transition elements form interstitial compounds.


(ii) Mn3+ (3d4) is strongly oxidising whereas Cr2+ (3d4) is strongly reducing.


(iii) Transition metals have high melting point.


(b) What is ‘Misch metal’? Write one use.


 26

Calculate emf and G for the following cell at 298 K

Mg (s)| Mg2+ (0.01M) || Ag+ (0.0001M) | Ag (s)


Given: E˚(Mg2+/Mg) = -2.37 V and E˚(Ag+/Ag) = +0.80 V


OR


(a) The conductivity of 0.001 mol/L solution of CH3COOH is 4.95 10-5 S/cm. Calculate it’s molar conductivity and degree of dissociation.


Given, (H+) = 349.6 S cm/mol


(CH3COO-) = 40.9 S cm/mol


(b) What is a fuel cell? Write its one advantage over the other ordinary cells.