35 Questions
Which of the following reagents is not commonly used in Lassaigne's test for nitrogen detection?
Potassium
What is the principle behind the detection of sulphur in an organic compound using sodium fusion?
Formation of sodium sulphide
What is the reagent used to detect the presence of water in a compound during sodium fusion?
Anhydrous copper sulphate
What is the purpose of sodium fusion in qualitative analysis of an organic compound?
To detect the presence of nitrogen, phosphorus, and halogens
Which of the following is not a step in Lassaigne's test for nitrogen detection?
Heating the compound with copper(II) oxide
What is the product formed when an organic compound containing nitrogen is fused with sodium?
Sodium amide
What is the product formed when phosphorus in an organic compound is oxidised?
H3PO4
What is the purpose of treating the phosphoric acid with magnesia mixture?
To form a precipitate of MgNH4PO4
Which of the following methods is not suitable for purifying a mixture of sugar and common salt?
Sublimation
What is the criterion for selecting a solvent in differential extraction?
The solvent should be immiscible with water and the organic compound should be highly soluble in it
Which of the following compounds can be purified using sublimation?
All of the above
What is the final product formed when the MgNH4PO4 precipitate is ignited?
Mg2P2O7
What is the primary purpose of sodium fusion in the detection of elements in an organic compound?
To convert the covalent form of the elements to their ionic form
What is the colour of the compound formed when Sodium hexacyanoferrate (II) reacts with Fe3+ ions?
Prussian blue
What is the purpose of boiling the fused mass with distilled water in Lassaigne's test?
To extract the cyanide, sulphide, and halide of sodium from the fused mass
What is the compound formed when CuO reacts with H2O?
CuO.H2O
What is the purpose of adding lead acetate to the Sodium Fusion Extract in the Lead Acetate Test?
To detect the presence of sulphur in the compound
What is the compound formed when Ca(OH)2 reacts with CO2?
CaCO3
What is the main difference between configurational isomers and conformational isomers?
Configurational isomers are different compounds, whereas conformational isomers are different spatial arrangements of the same compound.
What does a projection formula indicate?
The spatial arrangement of bonds in a molecule
What is the difference between the left and right conformers in the diagram?
The left conformer is in a stable position, while the right conformer is in an unstable position.
In a monosubstituted cyclohexane, which conformation is generally more stable?
The conformation with the substituent at equatorial position
What is torsional strain?
The strain that occurs when bonds are twisted out of their ideal shape
What is the main difference between conformational isomers and configurational isomers in terms of their energy?
Conformational isomers have lower energy than configurational isomers
What is the primary cause of the difference in energy between the two chair conformations of a monosubstituted cyclohexane?
1,3-Diaxial interaction
Which type of strain is responsible for the instability of the axial conformation in a monosubstituted cyclohexane?
1,3-Diaxial interaction
What is the main factor that determines the relative stability of conformers of cyclic systems?
Conformational energy
What is the effect of a substituent on the conformational energy of a monosubstituted cyclohexane?
It depends on the type of substituent
Which type of interaction is responsible for the energy difference between the axial and equatorial conformations of a monosubstituted cyclohexane?
1,3-Diaxial interaction
What is the relationship between the percentage of enol content and the stability of the alkene in Keto-Enol Tautomerism?
The percentage of enol content increases with the stability of the alkene.
What is the condition required for Tautomerism to occur?
The presence of an alpha-hydrogen atom
What is the type of Tautomerism that involves the movement of a hydrogen atom between two polyvalent atoms?
Keto-Enol Tautomerism
What is the term used to describe the isomers that differ in the arrangement of atoms in a chain?
Ring-Chain isomers
What is the type of isomerism that involves the movement of a hydrogen atom between two polyvalent atoms in a molecule?
Tautomerism
What is the factor that affects the percentage of enol content in Keto-Enol Tautomerism?
Polarity of the solvent
Study Notes
Acidic Strength
- The order of acidic strength is: PhSO3H > RSO3H > PhCOOH > RCOOH > OH > H > H2CO3 > HC ≅ HCN > CH3
- Point to remember: The acidic strength of dicarboxylic acids is COOH(CH2)nCOOH > COO-(CH2)nCOOH
- Ortho effect: C-OH > C-O-G > Feasibility of reaction: NaX + HY NaY + HX
Qualitative Analysis of an Organic Compound
- Identification of the elements present in an organic compound:
- Carbon and hydrogen: detected by heating the compound with copper(II) oxide
- Nitrogen: detected by heating the compound with copper(II) oxide and then testing with iron(II) sulphate
- Sulphur: detected by lead acetate test and sodium nitroprusside test
- Halogens: detected by sodium fusion extract
- Phosphorous: detected by heating the compound with copper(II) oxide and then testing with magnesia mixture
Purification
- Crystallisation: a saturated hot solution is allowed to cool, and the solute is no longer soluble in the solvent, forming crystals of the pure compound
- Sublimation: certain organic substances convert directly from solid to vapour state on heating and vice versa on cooling
- Differential Extraction: the process of separation of an organic compound from its aqueous solution by shaking it with a suitable organic solvent
Detection of Hydrogen
- Hydrogen is detected by heating the compound with copper(II) oxide and then testing with anhydrous copper sulphate
Organometallic Compounds
- Sodium fusion: extracts elements present in the compound from their covalent form to their ionic form by fusing the organic compound with sodium metal
- Lassaigne's test: cyanide, sulphide, and halide of sodium so formed on sodium fusion are extracted from the fused mass by boiling it with distilled water
Detection of Nitrogen
- Sodium fusion extract is boiled with iron(II) sulphate to form sodium hexacyanoferrate (II)
- On heating with sulphuric acid, some Fe2+ ions are oxidised to Fe3+ ions, which react with sodium hexacyanoferrate (II) to give Prussian blue colour of ferric ferrocyanide, confirming the presence of nitrogen
Conformations of Cyclohexane
- Ring flipping of cyclohexane: ⇌ ⇌ ⇌ ⇌ ⇌
- Energy profile diagram (3D)
- Conformations of monosubstituted cyclohexane: two different chair conformations, one with the substituent at axial position and the other with the substituent at equatorial position
- Conformations of polysubstituted cyclohexane: axial and equatorial positions
General Organic Chemistry
- Bond cleavage: homolytic and heterolytic cleavage
- Intermediates: carbocation, free radical, and carbanion
- Electron displacement effect: permanent and temporary effects
- Inductive effect: characteristics, +I effect, and -I effect
- Applications of inductive effect: intermediates, acid dissociation constant, and base strength
Resonance
- Resonance and resonating structures
- Resonance hybrid
- Conjugation: types of conjugation and extended conjugation
Classification of Isomers
- Isomers: structural (constitutional) and stereoisomers (space/3D)
- Configurational isomers: different compounds, e.g., cis and trans isomers
- Conformational isomers: different spatial arrangements of the same compound
- Projection formulae: indicates spatial arrangement of bonds
Tautomerism
- Diad and triad tautomerism
- Conditions for tautomerism: enol and keto forms
- Keto-enol tautomerism: examples and conditions
- Polarity of solvent affects keto-enol tautomerism
Degree of Unsaturation
- Formula: 𝛑 = (2n + 2 - h) / 2
- Remember: C=C > C≡C > C=O
Test your understanding of acidic strength in the periodic table, including the order of acidic strength, dicarboxylic acids, and the Ortho effect. This quiz covers key concepts and reactions in organic chemistry, including the feasibility of reactions with NaHCO3.
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