Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.
Estimation of halogens: It involves oxidising the organic substance with fuming nitric acid in the presence of silver nitrate. The halogen of the substance is thus converted to silver halide which is separated and weighed:
1Weight of organic compound = W gm
weight of silver halide = x g.
Estimation of sulphur: The organic substance is heated with fuming nitric acid but no silver nitrate is added. The sulphur of the substance is oxidised to sulphuric acid which is then precipitated as barium sulphate by adding excess of barium chloride solution. From the weight of BaSO4 so obtained the percentage of sulphur can be calculated.
Estimation of phosphorous: The organic substance is heated with fuming nitric acid whereupon phosphorous is oxidised to phosphoric acid. The phosphoric acid is precipitated as ammonium phosphomolybdate, (NH4)3 PO4 .12MOO3, by the addition of ammonia and ammonium molybdate solution which is then separated, dried and weighed.
Classify the following reactions in one of the reaction type studied in this unit.
(a) CH3CH2Br + HS– ———–> CH3CH2SH + Br–
(b) (CH3)2C=CH2 + HCl ———–> (CH3)2CCl—CH3
(c) CH3CH2Br + HO– ———–> CH2=CH2 + H2O + Br–
(d) (CH3)3C—CH2OH + HBr ———–> (CH3)2 C Br CH2CH2CH3 + H2O
Name a suitable technique of separation of the components from a mixture of calcium sulphate and camphor.
In which of the following compounds the carbon marked with asterisk is expected to have greatest positive charge?
Why is it necessary to use acetic acid and not sulphric acid for acidification of sodium extract for testing sulphur by lead acetate test?
The IUPAC name for
(a) 1-Hydroxypentane-l, 4-dione
(b) 1,4-Dioxopentanol
(c) l-Carboxybutan-3-one
(d) 4-Oxopentanoic acid
Describe the method, which can be used to separate two compounds with different solubilities in a solvent S.
Explain hyperconjugation effect. How does hyperconjugation effect explain the stability ofalkenes?
In the Lassaigne’s test for ntrogen in an organic compound, the Prussian blue colour is obtaine d due to the formation of:
(a) Na4[Fe(CN)6] (b)Fe4[Fe(CN)6]3
(c) Fe2[Fe(CN)6] (d)Fe3[Fe(CN)6]4 .
(a) 1 -Chloro-2-nitro-4-methylbenzene
(b) l-Chloro-4-methyl-2-nitrobenzene
(c) 2-Chloro-1 -nitro-5-methylbenzene
(d) m-Nitro-p-chlorotoluene
Covalent bonds can undergo fission in two different ways. The correct representation involving the heterolytic fission of CH3 – Br is
Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.
0 .12 g of an organic compound containing phosphorous gave 0.22 g of Mg2 P2O7 by usual analysis. Calculate the percentage of phosphorous in the compound.
(a) 2-Ethyl-3-methylpentane
(b) 3,4-Dimethylhexane
(c) 2-sec-Butylbutane
(d) 2,3-Dimethylbutane
Two or more compounds having same the molecular formula but different functional groups are called functional isomers. Which of die following pairs are not functional group isomers?
(a) II and III (b) II and IV
(c) I and IV (d) I and II
The structure of triphenylmethyl cation is given here. This is very stable and some of its salts can be stored for months. Explain the cause of high stability of this cation
Which of the following represents the correct TUPAC name for the compounds concerned?
(a) 2, 2-Dimethylpentane or 2-Dimethylpentane (b) 2, 4, 7-Trimethyloctane or 2, 5, 7- Trimethyloctane (c) 2-Chloro-4-methylpentane or 4-Chloro-2-methylpentane (d) But-3-yn- l-ol or But-4-ol-yne.
Give a brief description of the principles of the following techniques taking an example in each case: (a) Crystallisation (b) Distillation (c) Chromatography
Suggest a suitable technique for separating naphthalene from kerosene oil present in a mixture.
Write the name of element which is confirmed on adding Na2[Fe(CN)5NO] in sodium extract solution due to appearance of violet colouration.
(a) What do you understand by Homolytic fission?
(b) What are carbanions? Give an example.
Why is an organic compound fused with Sodium for testing nitrogen, halogens and sulphur?
Electronegativity of carbon atoms depends upon their state of hybridization. In which of the following compounds, the carbon marked with asterisk is most electronegative?
Compounds with same molecular formula but differing in their structures are said to be structural isomers. What type of structural isomerism is shown by
Resonance structures of propenal are given below. Which of these resonating structures is more stable? Give reason for your answer.
What are hybridisation states of each carbon atom in the following compounds? CH2=C=O, CH3CH=CH2, (CH3)2CO, CH2=CHCN, C6H6.
Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation ?
What are electrophiles? Explain electrophile substitution reaction with the help of example.
By mistake, an alcohol (boiling point 97 °C) was mixed with a hydrocarbon (boiling point 68 °C). Suggest a suitable method to separate the two compounds. Explain the reason for your choice.
Match Column I with Column II.
| Column I | Column II |
| (a) Dumas method | (1) AgN03 |
| (b) Kjeldahl method | (2) Silica gel |
| (c) Carius method | (3) Nitrogen gel |
| (d) Chromatography | (4) Free radicals |
| (e) Homolysis | (5) Ammonium sulphate |
Indicate the a- and n-bonds in the following molecules:
C6H6 , C6H12, CH2Cl2, CH=C=CH2, CH3NO2, HCONHCH3
Draw formulas for the first five members of each homologous series beginning with the following compounds,
(a) H—COOH (b) CH3COCH3 (c) H—CH=CH2
Identify the reagents shown in bold in the following equations as nucleophiles or electrophiles
(a) CH3COOH + HO– ———–> CH3COO– + H2O
(b) CH3COCH3 + CN ———–> (CH3)2 C(CN)(OH)
(c) C6H5 + CH3CO ———–> C6H5COCH3
