Q: The major product formed in the following reaction is

In first step strong base NH 2 − will react with terminal alkyne. And in 2 nd step Birch reduction reaction will take place and give trans alkene.

Question 1

In the following reaction sequence, Q , R , S and T are the major products. The correct statement(s) about Q , R , S and T is(are)

Accepted Answer

Kolbe's electrolysis of sodium butyrate ( CH _3 CH _2 CH _2 COONa ) yields n-hexane. Aromatization of n-hexane using V _2 O _5 at 500^ C produces benzene (Q). Benzene (Q) reacts with phthalic anhydride in the presence of anhydrous AlCl _3 to form o-benzoylbenzoic acid (R). Treatment of R with PCl _5 gives o-benzoylbenzoyl chloride, which upon Rosenmund reduction ( H _2- Pd/BaSO _4) yields o-benzoylbenzaldehyde (S). Condensation of S with hydrazine ( NH _2 NH _2) forms 1-phenylphthalazine (T). Ev

Question 2

Treatment of buta-1,3-diyne with NaNH _2 (2 equivalents), followed by reaction with excess of trans- CH _3 -CH=CH-CH _2 -Br gives X as the major product. The maximum number of carbon atoms that are co

Accepted Answer

Buta-1,3-diyne (HC C - C CH) reacts with 2 equivalents of NaNH _2 to undergo double deprotonation, forming the acetylide dianion: HC C - C CH + 2 NaNH _2 \ ^ C C - C C ^ + 2 NH _3 This dianion acts as a strong nucleophile and undergoes an S_N2 reaction with the primary allylic halide, trans- CH _3 -CH=CH-CH _2 -Br (excess ensures both sides react): ^ C C - C C ^ + 2 CH _3 -CH=CH-CH _2 -Br CH _3 -CH=CH-CH _2 - C C - C C - CH _2 -CH=CH-CH _3 In the major product X , the central diyne unit consists

Question 3

The List-II contains products obtained from the reaction of compounds in List-I with O _3/Zn- H _2 O followed by cyclization (via more stable enolate) in the presence of aqueous NaOH. Match each entry

Accepted Answer

The given reaction sequence involves ozonolysis of the bicyclic alkenes followed by an intramolecular aldol condensation. For compound (P), the structure is a 6,6-fused system (an octalin derivative) with methyl groups on opposite sides of the double bond. Ozonolysis cleaves the central double bond to form a 10-membered ring 1,6-diketone with methyl groups at the -positions (C2 and C7). The base-catalyzed aldol condensation proceeds via the more stable trisubstituted enolate at C2, which attacks

Question 4

Natural rubber on complete ozonolysis ( O _3/Zn- H _2 O ) gives compound X as the major product. X gives positive iodoform and Tollen's tests. X on heating with aqueous NaOH gives Y as the major produ

Accepted Answer

Natural rubber is cis-1,4-polyisoprene, with the repeating unit [- CH _2- C ( CH _3)= CH - CH _2-]_n. Complete reductive ozonolysis ( O _3/Zn- H _2 O ) of natural rubber cleaves the double bonds to give 4-oxopentanal (levulinaldehyde) as compound X. [- CH _2- C ( CH _3)= CH - CH _2-]_n O _3/ Zn-H _2 O n CH _3- C (= O )- CH _2- CH _2- CHO Compound X ( CH _3- CO - CH _2- CH _2- CHO ) has a methyl ketone group, which gives a positive iodoform test, and an aldehyde group, which gives a positive Toll

Question 5

The option(s) with correct sequence of reagents for the conversion of P to Q is(are) :

Accepted Answer

Answer option index: 3

Question 6

The number of isomeric tetraenes (NOT containing sp-hybridized carbon atoms) that can be formed from the following reaction sequence is _____ .

Accepted Answer

The anti-addition of hydrogen to an alkyne pi bond occurs when reacted with sodium or lithium metal dissolved in ammonia. This reaction produces a trans-alkene as its product. Bromine react with alkene to give anti addition dibromo product. In this case both double bonds will react. In the next reaction elimination of HBr will take place forming tetraene. The final tetraene product can show Geometrical isomerism along one double bond only. So, it will have two isomers only.

Question 7

The number of - CH 2 - (methylene) groups in the product formed from the following reaction sequence is _____ .

Accepted Answer

The first reaction is called reductive ozonolysis in which alkene is converted into aldehyde of ketones. In 2nd reaction aldehyde group will be oxidised to carboxylic acid.  The third reaction is called Kolbe's electrolysis reaction in which decarboxylation reaction will occur forming higher alkane. In last step of reaction aromatisation reaction will take place forming benzene as the major product. This benzene does not contain any  CH 2  group.

Question 8

The reaction sequence(s) that would lead to o -xylene as the major product is(are)

Accepted Answer

Answer option index: 1

Question 9

The major product formed in the following reaction is

Accepted Answer

In first step strong base  NH 2 &#8722;  will react with terminal alkyne. And in  2 nd  step Birch reduction reaction will take place and give trans alkene.

Hydrocarbons — Previous Year Questions & Solutions