Chapter 12 - Organic Chemistry – Some Basic Principles and Techniques

Write the chemical composition of the compound formed when ferric chloride
is added containing both N and S.

Ammonia produced when 0.75g of a substance was kjeldahlized, neutralized
30cm³ of 0.25 N H₂SO₄. Calculate the percentage of nitrogen in the compound.

0.12g of organic compound containing phosphorus gave 0.22g of Mg₂P₂O₇ by

the usual analysis. Calculate the percentage of phosphorus in the compound

0.40g of an organic compound gave 0.3g of Ag Br by Carious method. Find the
percentage of bromine in the compound.

0.395 g of an organic compound by Carius method for the estimation of

sulphur gave 0.582 g of BaSO₄. Calculate the percentage of sculpture in the

compound.

Can you use calcium in place of sodium for fusing an organic compound?

Can you use potassium in place of sodium for fusing an organic compound in
Lassaigne’s test?

In which C – C bond of CH₃CH₂CH₂Br, the inductive effect is expected to be the

least?

How will you separate a mixture of two organic compounds which have
different solubility’s in the same solvent?

What is the basic principle of chromatography?

Name two methods which can be safely used to purify aniline.

Lasaigne’s test is not shown by diazonium salts. Why?

A liquid (1.0g) has three components. Which technique will you employ to
separate them?

Without using column chromatography, how will you separate a mixture of
camphor and benzoic acid?

Which technique can be used for purification of iodine that contains traces of
NaCl?

How can the mixture of kerosene oil and water be separated?

Will C Cl₄ give white precipitate of Ag Cl on heating it with Ag NO₃?

Name the common techniques used for purification of organic compounds.

Draw the orbital diagram showing hyperconjugation in ethyl cation

Show how hyper conjugation occurs in propene molecule.

Explain why is (CH₃)₃ C⁺ more stable than CH₃CH₂+ and CH₃⁺ is the least stable cation.

Draw the resonance structures for the following compounds

(a) C₆H₅OH (b) C₆H₅ – ⁺CH₂

Write the resonance structures of

(a) CH₃ NO₂ (b) CH₃ COO^-

Write resonance structures of

(a) CH₃COO- (b) C₆H₅NH₂.

Write resonance structures of CH₂ = CH – CHO. Indicate relative stability of

the contributing structure

Benzyl carbonation is more stable than ethyl carbonation. Justify.

Using curved – arrow notation, show the formation of reactive intermediates

when the following covalent bond undergo heterolysis cleavage.

(a) CH₃ – SCH₃, (b) CH₃ – CN, (c) CH₃ – Cu.

Identify electrophilic centre in the following: CH₃C H O_,CH₃C,CH₃I.

What are the nucleophiles?

Define carbocation.

Define heterolytic cleavage.

How many isomers are possible for monosubstituted and disubstituted
benzene?

Which of the following shows geometrical isomerism?

(a) CH Cl = CH Cl (b) CH₂ = C Cl₂ (c) C Cl₂ = CH Cl.

Alkynes does not exhibit geometrical isomers. Give reason.

How many structural isomers and geometrical isomers are possible for a
cyclohexane derivative having the molecular formula C₈H₁₆?

Name the chain isomers of C₅H₁₂ which has a tertiary hydrogen atom.

Draw the two geometrical isomers of, σ but – 2 – en – 1, 4 dioic acid. Which of
the will have higher dipole movement?

What is the cause of geometrical isomerism in alkenes?

Derive the structure of 3 – Nitrocyclohexene.

Write the structural formula of
(a) p – Nitro aniline (b) 2,3 – Dibromo-1-phenylpentane.

Name the chain isomers of C₅H₁₂ which has a tertiary hydrogen atom.

Write an example of alicyclic compound

Write an example of non – benzenoid compound

Give two examples of aliphatic compounds

Define homologous series?

What is a functional group?

How are organic compounds classified?

Why are electrons easily available to the attacking reagents in π – bonds?

How many σ and π bonds are present in each of the following molecules?

(a) HC≡CCH≡CHCH₃ (b) CH₂=C=CHCH₃.

What is the shape of the following molecules:

(a) H₂ C=O (b) CH₃F (c) HC≡N.

What type of hybridization of each carbon atom in the following compounds?

(a) CH₃Cl (b) (CH₃)₂CO (c) CH₃CN (d) CH₃CH = CHCN.

Why is sp hybrid orbital more electronegative than sp2 or sp3 hybridized
orbitals?

How does hybridization affect the electronegativety ?

Write the expanded form of the following condensed formulas into their

complete structural formulas.

(a) CH₃CH₂COCH₂CH₃.

(b) CH₃CH=CH(CH₂)₃CH₃.

The reaction:

is classified as :

(a) electrophilic substitution (b) nucleophilic substitution

(c) elimination (d) addition

The best and latest technique for isolation, purification and separation of organic compounds is:

(a) Crystallisation (b) Distillation (c) Sublimation (d) Chromatography

Which of the following carbocation is most stable?

(a) (b)  (c) 

(d) 

In the Lassaigne's test for nitrogen in an organic compound, the Prussian blue colour is obtained 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

In the organic compound CH₂=CH-CH₂-CH₂-C≡CH, the pair of hydridised orbitals involved in the formation of: C₂ - C₃ bond is:

(a) sp - sp²(b) sp - sp³(c) sp² - sp³ (d) sp³- sp³

In the estimation of sulphur by Carius method, 0.468 g of an organic sulphur compound afforded 0.668 g of barium sulphate. Find out the percentage of sulphur in the given compound.

0.3780 g of an organic chloro compound gave 0.5740 g of silver chloride in Carius estimation. Calculate the percentage of chlorine present in the compound.

A sample of 0.50 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.5 M H₂SO₄. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. Find the percentage composition of nitrogen in the compound.

Why is it necessary to use acetic acid and not sulphuric acid for acidification of sodium extract for testing sulphur by lead acetate test?

Why is a solution of potassium hydroxide used to absorb carbon dioxide evolved during the estimation of carbon present in an organic compound?

Will CCl₄ give white precipitate of AgCl on heating it with silver nitrate? Give reason for your answer.

Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation?

Name a suitable technique of separation of the components from a mixture of calcium sulphate and camphor.

Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen, sulphur and halogens.

Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?

Explain the principle of paper chromatography.

Discuss the principle of estimation of halogens, sulphur and phosphorus present in an organic compound.

Differentiate between the principle of estimation of nitrogen in an organic compound by (i) Dumas method and (ii) Kjeldahl's method.

Discuss the chemistry of Lassaigne's test.

What is the difference between distillation, distillation under reduced pressure and steam distillation ?

Describe the method, which can be used to separate two compounds with different solubilities in a solvent S.

Give a brief description of the principles of the following techniques taking an example in each case.

(a) Crystallisation (b) Distillation (c) Chromatography

Explain the terms Inductive and Electromeric effects. Which electron displacement effect explains the following correct orders of acidity of the carboxylic acids?

(a) Cl₃CCOOH > Cl₂CHCOOH > ClCH₂COOH

(b) CH₃CH₂COOH > (CH₃)₂CHCOOH > (CH₃)₃C.COOH

For the following bond cleavages, use curved-arrows to show the electron flow and classify each as homolysis or heterolysis. Identify reactive intermediate produced as free radical, carbocation and carbanion.

What is the relationship between the members of following pairs of structures? Are they structural or geometrical isomers or resonance contributors?

(a)

(b)

(c)

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)₂ClC-CH₃

(c) CH₃CH₂Br + HO^- → CH₂ = CH₂ + H₂O + Br^-

(d) (CH₃)₃C - CH₂OH + HBr → (CH₃)₂CBrCH₂CH₃+ H₂O

Identify the reagents shown in bold in the following equations as nucleophiles or electrophiles:

What are electrophiles and nucleophiles? Explain with examples.

Draw the resonance structures for the following compounds. Show the electron shift using curved-arrow notation.

(a) C6H5OH (b) C6H5NO2 (c) CH3CH = CH – CHO

(d) C6H5CHO (e) (f) 

Explain why alkyl groups act as electron donors when attached to a Ã€ system.

Which of the two: O₂NCH₂CH₂O^- or CH₃CH₂O^- is expected to be more stable and why?

Identify the functional groups in the following compounds

(a)

(b)

(c)

Give condensed and bond line structural formulas and identify the functional group(s) present, if any, for :

(a) 2,2,4-Trimethylpentane

(b) 2-Hydroxy-1,2,3-propanetricarboxylic acid

(c) Hexanedial

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

Which of the following represents the correct IUPAC 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-1-ol or But-4-ol-1-yne

Give the IUPAC names of the following compounds:

(a)

(b)

(c)

(d)

(e)

(f) Cl₂CHCH₂OH

Write bond line formulas for: Isopropyl alcohol, 2,3-Dimethyl butanal, Heptan-4-one.

Indicate the ÃÆ’ and Ã€ bonds in the following molecules:

C₆H₆, C₆H₁₂, CH₂Cl₂, CH₂ = C = CH₂, CH₃NO₂, HCONHCH₃

What are hybridisation states of each carbon atom in the following compounds?

CH₂=C=O, CH₃CH=CH₂, (CH₃)₂CO, CH₂=CHCN, C₆H₆