Chemystry

Hydrocarbons

100

A camping stove uses propane (C₃H₈).

If 44 g of propane is completely burned:

C₃H₈+5O₂→3CO₂+4H₂O
How many grams of CO₂ are produced?   

132 g CO₂

200

Why does acetylene (C₂H₂) produce a hotter flame than methane (CH₄)?

Acetylene has a triple bond (higher energy).
It releases more energy during combustion → hotter flame (~3300°C)

300

Why doesn’t benzene undergo addition reactions easily like alkenes?

Because benzene is aromatic and very stable (Hückel rule: 4n+2 π electrons).
Addition would destroy aromatic stability.

400

In darkness I am silent and slow, But under UV light I start to glow. Chlorine splits — radicals appear, They attack methane without fear. Initiation, propagation, termination too, Chain reaction — I continue through. Who am I?

• Reaction: Chlorination of methane

• Mechanism: Free radical substitution

• Initiation step: Cl₂ → 2Cl• (homolytic cleavage)

500

You nitrate toluene using HNO₃/H₂SO₄.

❓ Tasks:

1. Predict major products.

2. Explain directing effect.(Mechanism)

1. ortho-nitrotoluene

• para-nitrotoluene

2. Electrophilic aromatic substitution

Heterocycles

100

Electrophilic substitution in pyrrole occurs mainly at which position — 2 or 3? Why?

Position 2 (α-position)
More resonance stabilization of sigma complex.

200

Which is most sensitive to acidic conditions: pyrrole, furan, or thiophene?

Furan (least aromatic stability).

300

Suggest a method to synthesize pyrrole from a 1,4-dicarbonyl compound.

Paal–Knorr synthesis

400

• Which 5-membered heterocycle is present in:

  • Vitamin B1 (Thiamine)?

Tiazol

500

Which 5 membered heterocyle is available in Korrin Porfin va Billuribin?

Pyrrole

X-questions

100

Why Does Onion Make You Cry?

Onions release sulfur-containing compounds (e.g., sulfoxides).
When cut, they form a volatile compound that reacts with water in your eyes to produce a mild acid → irritation and tears.

200

Why Is Paracetamol Less Acidic Than Aspirin?

Aspirin contains a carboxylic acid (-COOH) group → strongly acidic.
Paracetamol contains a phenol (-OH) group → weaker acid.

Carboxylic acids are more acidic because their conjugate base is more resonance stabilized.

300

Why Is Soap Able to Remove Oil?

Soap molecules have:

• Long nonpolar hydrocarbon tail

• Polar carboxylate head

They form micelles, trapping oil inside.
Interaction involved: Hydrophobic interaction.

400

Why Does Cooking Meat Produce Aroma?

• Amino groups (proteins)

• Carbonyl groups (sugars)

• This produces complex aromatic organic compounds responsible for flavor.

500

Why Does DNA Contain Nitrogen Heterocycles?

Nitrogen heterocycles (purines & pyrimidines):

• Are aromatic → stable

• Form hydrogen bonds

• Enable specific base pairing

Aromaticity contributes to structural stability of DNA.

Rhyming style

100

I’m made of ethene, long and strong, I last forever — don’t come along! Which polymer chain am I in the throng?

Polyethylene

200

I dissolve polish in a flash, My carbonyl group does the dash. Which solvent am I in your stash?

Acetone (ketone –C=O)

300

I fight radicals, keep cells free,
I donate electrons, that is me.
Which vitamin am I, can you see?

Vitamin C (ascorbic acid)

400

C–F bonds make me tough,
Nothing sticks — that’s enough.
Which polymer surface is this stuff?

Teflon (PTFE)

500

I’m in syrups and candies too,
I taste like sugar, but I’m not you.
Which polyol keeps desserts sweet through?

Glycerol (–OH groups / sugar alcohol)