This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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To determine the number of geometrical isomers (cis-trans isomers), we need to identify the number of double bonds that can exhibit cis-trans isomerism. A double bond can show cis-trans isomerism if each carbon atom of the double bond is attached to two different groups. For a molecule with n different double bonds capable of cis-trans isomerism, the maximum number of geometrical isomers is 2^n. However, if the molecule is symmetrical, the number of isomers might be less than 2^n. Step 1: Analyze molecule (i) CH_3-CH=CH-CH=CH-CH_3. This molecule has two double bonds. Let's label them as C_2=C_3 and C_4=C_5. • For C_2=C_3: The C_2 is attached to CH_3 and H. The C_3 is attached to H and CH=CH-CH_3. Both carbons have two different groups, so this double bond can exhibit cis-trans isomerism. • For C_4=C_5: The C_4 is attached to CH_3 and H. The C_5 is attached to H and CH=CH-CH_3. Both carbons have two different groups, so this double bond can exhibit cis-trans isomerism. This molecule is symmetrical. The general formula for the number of geometrical isomers for a symmetrical polyene with n double bonds is 2^n-1 + 2^(n/2)-1 if n is even. Here, n=2. Number of isomers = 2^2-1 + 2^(2/2)-1 = 2^1 + 2^1-1 = 2^1 + 2^0 = 2 + 1 = 3. The three isomers are: 1. cis, cis 2. trans, trans 3. cis, trans (which is identical to trans, cis due to symmetry) Step 2: Analyze molecule (ii) CH_3-CH=CH-CH=CH-Cl. This molecule also has two double bonds. Let's label them as C_2=C_3 and C_4=C_5. • For C_2=C_3: The C_2 is attached to CH_3 and H. The C_3 is attached to H and CH=CH-Cl. Both carbons have two different groups, so this double bond can exhibit cis-trans isomerism. • For C_4=C_5: The C_4 is attached to H and CH=CH-CH_3. The C_5 is attached to H and Cl. Both carbons have two different groups, so this double bond can exhibit cis-trans isomerism. This molecule is unsymmetrical. For an unsymmetrical polyene with n double bonds, the number of geometrical isomers is 2^n. Here, n=2. Number of isomers = 2^2 = 4. The four isomers are: 1. cis, cis 2. cis, trans 3. trans, cis 4. trans, trans Step 3: Compare with the given options. Molecule (i) has 3 geometrical isomers. Molecule (ii) has 4 geometrical isomers. The correct option should be 3 and 4. The final answer is (4) 3 and 4. Drop the next question.