31 Year NEET Questions: Some Basic Principles And Techniques- 4 - NEET MCQ

Five chain isomers are possible which are –

The compound containing a chiral carbon atom i.e., (a carbon atom which is attached to four different substituents is known as a chiral carbon atom) is optically active.

Tetrachloroethene being an alkene has sp2 -hybridized C– atoms and hence the angle Cl – C – Cl is 120° while in tetrachloromethane, carbon is sp3 hybridized, therefore the angle Cl – C – Cl is 109.5°.

All the properties mentioned in the question suggest that it is a benzene molecule. Since in benzene all carbons are sp²–hybridized, therefore, C – C – C angle is 120°

Nitrogen, sulphur and halogens are tested in an organic compound by Lassaigne's test.
The organic compound is fused with sodium metal as to convert these elements into ionisable inorganic substances,

The cyanide, sulphide or halide ions can be confirmed in aqueous solution by usual test.

Such isomers, which possess the same molecular and structural formula but differ in the arrangement of atoms around the double bonded carbon atoms are known as geometrical  isomers.

Kjeldal's method is suitable for estimating nitrogen in those compounds in which nitrogen is linked to carbon and hydrogen.
The method is not used in case of nitro, azo and azoxy compound. This method is basically used for estimating nitrogen in food fertilizers and agricultural products.

Hence it is homocyclic (as the ring system is made of one type of atoms, i.e. carbon) but not aromatic.As it does not have (4n +2)π electron required for aromaticity.

Sodium cyanide (Na + C + N → NaCN). (Lassaigne's test)

Shortest C – C distance (1.20 Å) is in acetylene.
As acetylene has sp hybridisation, the bond length increases in the order

sp³ orbital has 1/4(25%) s-character. & 75% p character.

Organic compounds having same molecular formula but differ from each  other in physical properties or chemical properties or both are known as isomers.

Higher the possibility of delocalisation of the positive charge, greater is stability of the species. Thus

Benzyl carbocation is more stable than tertbutyl due to resonance in the former.

Carboxylic acids dissolve in NaHCO₃ but phenols do not.

2-Methyl-2-butene

4-Hydroxy-2-methylpent-2-en-1-al

Angle increases progressively sp³ ( 109°28' ), sp² (120°), sp (180°)

Due to + I-effect of the CH₃ group, toluene has much higher electron density in the ring than benzene, nitrobenzene and benzoic acid as nitro and carboxylic group show- I-effect and hence toluene is most reactive towards nitration.

Resonance structures are separated by a double headed arrow 

Rotation around π bond is not possible. If any attempt is made to rotate one of the carbon atoms, the lobes of π-orbital will no longer remain coplanar i.e no parallel overlap will be possible and thus π-bond will break .
This is known as concept of restricted rotation. In other words the presence of π-bonds makes the position of two carbon atom.

Diastereomers since they have different melting points, boiling points, solubilities etc.

Resolution

Such questions can be solved by considering the relative basic character of their conjugated bases which for H₂O, C₂H₂, H₂CO₃ and C₆H₅OH are

More the possibility for the dispersal of the negative charge, weaker will be the base.
Thus the relative basic character of the four bases is

Thus the acidic character of the four corresponding acids wil be

Chlorination of methane proceeds via free radical mechanism. Conversion of methyl chloride to methyl alcohol proceeds via nucleophilic substitution. Formation of ethylene from ethyl alcohol proceeds via dehydration reaction. Nitration of benzene is electrophilic substitution reaction.

3-Ethyl-2-methylpentane

Hydrazine (NH₂NH₂) does not contain carbon and hence on fusion with Na metal, it cannot form NaCN; consequently hydrazine does not show Lassaigne’s test for nitrogen.

The boiling point of o-nitrophenol is less than para-nitrophenol due to presence of intramolecular hydrogen bonding. Since p-nitrophenol is less volatile in than onitrophenol due to  presence of inter molecular hydrogen bonding hence they can be separated by steam distillation.

The vital force theory suffered first death blow in 1828 when Wohler synthesized the Ist organic compound urea in the laboratory from inorganic compounds reported below :

Later on a further blow to vital force theory was given by Kolbe (1845) who prepared acetic acid, the first organic compound, in laboratory from its elements.