CheMentor Doubt Portal

Temperature in numerical problems = always Kelvin, not Celsius.

Structure: DNA double, RNA single

Sugar: DNA deoxyribose, RNA ribose

Bases: DNA (A,T,G,C), RNA (A,U,G,C)

Function: DNA stores, RNA synthesizes protein

Location: DNA nucleus, RNA nucleus + cytoplasm

Stability: DNA stable, RNA less stable

Answer: Increasing Basicity order is
o-hydroxyaniline < m-hydroxyaniline < aniline < p-hydroxyaniline

🧩 Ortho (o-) → Least basic
- Intramolecular H-bonding locks –NH₂

- Lone pair not free → ↓ basicity

🧩 Meta (m-) → Slightly low
- No resonance donation from –OH
- Only weak effect → slightly less than aniline

🧩 Aniline → Reference
- Normal availability of lone pair

🧩 Para (p-) → Most basic
- –OH shows +R effect (electron donation)
- Pushes electrons toward –NH₂ → ↑ basicity

The unit of pseudo-first order rate constant is the same as a first-order reaction, i.e., s⁻¹ (per second)

Main reasons:
1. Atomic size increases
Outer electron is farther from nucleus
→ weaker attraction

2. Shielding effect increases
More inner shells block nuclear pull
→ effective nuclear attraction decreases

3. Less energy needed
Electron is loosely held
→ ionisation potential decreases

Bigger atom + more shielding = lower ionisation potential

Example:
Group 1:
Li > Na > K > Rb > Cs (I.P decreases downwards)

No, [Co(H2O)6]Cl2 does not show solvate isomerism.

Reason:
Solvate isomerism requires the presence of solvent molecules both inside and outside the coordination sphere so that interchange is possible. In [Co(H₂O)₆]Cl₂, all six H₂O molecules are coordinated to Co²⁺ and no water molecule is present outside the coordination sphere. Hence, no rearrangement is possible.

Conclusion:
Absence of external solvent molecules ⇒ No solvate isomerism.

From the ISC Class XII syllabus (Electrochemistry)
Diagrams of dry cell, primary cells, fuel cells → NOT required

Focus is on →
- Working principle
- Anode, cathode
- Half & overall reactions
- Reasoning questions

👉 Exam tip:
Practicing diagrams not required, but read the diagrams, master reactions + concepts

Thank you

Stability = how well the charge/electron density is dispersed.
More dispersion → more stability.

Carbocation stability order: 3° > 2° > 1° > CH₃⁺

Why?
1. +I effect (alkyl groups donate electrons) → stabilizes positive charge

2. Hyperconjugation → “no. of α-H” increases stability

3. Resonance (if present) → enhances stability greatly

Special cases:
- Allylic & Benzylic carbocations → very stable (resonance)
- Vinylic carbocation → very unstable

Primary alcohols on controlled oxidation with mild oxidizing agents like PCC form aldehydes. The reaction involves removal of hydrogen atoms from the –OH group and adjacent carbon. Strong oxidants must be avoided as they further oxidize aldehydes to carboxylic acids.

1. Oxidation in the presence of K2Cr2O7
2. Alcohol heated at 573K in the presence copper

Catalytic oxidation of hydrocarbons like alkanes would give a series of alcohol, aldehyde and carboxylic acid

A carbocation is an organic ion in which a carbon atom carries a positive charge.
​
Key Features:
- Carbon has only 6 electrons → electron-deficient
- Positive charge on carbon atom
- sp² hybridised
- Trigonal planar shape (120°)

Contains an empty p-orbital → makes it highly reactive

Positively charged carbon species

Dichlorocarbene

C

Variable valency is the ability of an element to show more than one valency (combining capacity).

Why it happens
- Due to loss of different number of electrons
- Common in transition metals

Examples:
a) Iron (Fe) → Fe²⁺ and Fe³⁺
b) Copper (Cu) → Cu⁺ and Cu²⁺

Transition elements show the property of variable valency as they lose one or more electron from their penultimate shell due to overcrowding of e- OR internal atomic electron repulsion

You can learn these mechanisms from YouTube (search “reaction mechanism step by step”) where concepts are explained visually.
You can also use Khan Academy, which gives simple and clear explanations suitable for Class XII students.

A nucleophile is a species that donates a pair of electrons to form a bond.

Key Points:
- Rich in electrons (has lone pairs or negative charge)
- Attacks positive or electron-deficient centers
- Acts as a Lewis base

Examples:
OH⁻, CN⁻, NH₃, Cl⁻

Aldehydes are converted to primary alcohols by reduction using agents like NaBH₄ or LiAlH₄.
Hydrogen adds to the carbonyl group, converting –CHO into –CH₂OH.

Aldehydes are converted to primary alcohols by reduction (addition of hydrogen).