Q.(a) What is Lindlar's catalyst? (½)

Ozonolysis cleaves a C=C double bond and replaces it with two C=O groups. For but-2-ene, the double bond is cleaved right at its centre, giving two identical carbonyl fragments.

But-2-ene: CH3-CH=CH-CH3

Step 1: Ozone (O3) adds across the C=C double bond to form an ozonide intermediate.

Step 2: Reductive workup with Zn/H2O cleaves the ozonide, converting each carbon that was part of the double bond into a C=O (carbonyl) group, while any H originally on that carbon is retained.

Each of the two double-bonded carbons in but-2-ene carries one H and one CH3 group. After cleavage, each becomes CH3-CHO (ethanal/acetaldehyde).

So but-2-ene --(i) O3, …

Ozonolysis splits a C=C double bond exactly at the bond, converting each sp2 carbon into a C=O carbonyl carbon; propene's two different ends give two different carbonyl products, ethanal and methanal.

Ozonolysis is a reaction where an alkene's C=C double bond is cleaved by ozone (O3) followed by reductive workup (e.g. Zn/H2O), converting each carbon of the double bond into a carbonyl group (C=O), with the identity of the carbonyl (aldehyde vs ketone) depending on how many H atoms/alkyl groups were originally on that carbon.

Propene structure: CH3-CH=CH2

The double bond is between C2 and C3 (using CH3 as C1): CH3-CH(=)-CH2(=)

Ozonolysis cleaves exactly at this C=C bond, converting each carbon into its own carbonyl compound:

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Ozonolysis breaks the C=C double bond and replaces it with C=O on each fragment; since ethene's carbons are both CH2 groups, cleavage gives two identical methanal (formaldehyde) molecules.

Ozonolysis is a reaction where an alkene's C=C double bond is cleaved by ozone (followed by reductive workup, typically with Zn/H2O), converting each doubly-bonded carbon into a carbonyl (C=O) carbon.

Ethene: CH2=CH2

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The drawn alkene is pent-2-ene, CH3-CH=CH-CH2-CH3. Ozonolysis (O3, then H2O) cleaves the C=C bond, giving acetaldehyde (CH3CHO) and propanal (CH3CH2CHO) as compound B.

Pent-2-ene, CH3-CH=CH-CH2-CH3, has its double bond between C2 and C3. Ozonolysis cleaves exactly at the C=C bond, turning each doubly-bonded carbon into a C=O: the C1-C2 fragment becomes ethanal (CH3-CHO) and the C3-C4-C5 fragment becomes propanal (CH3-CH2-CHO).

Pent-2-ene structure, numbered: C1H3-C2H=C3H-C4H2-C5H3.

Ozonolysis (O3 then Zn/H2O reductive workup) cleaves the C=C double bond, converting each alkene carbon into a carbonyl carbon (C=O), while the rest of each fragment's chain and hydrogens stay as they were:

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