Question

Match the following: \(\begin{array}{ll}\text { List 1 } & \text { List 2 }\end{array}\) 1\. Benzene (1) Phosgene 2\. Ethylene (2) Silver mirror 3\. Acetaldehyde (3) Mustard gas 4\. Chloroform (4) \((4 n+2) \pi\) -electrons (5) Carbylamine The correct matching is: 1 2 4 (a) (4) (3) (1) (2) (b) (4) (3) \((2)\) (c) (3) (4) (2) (1) (d) (2) (1) (4)

Short answer

Option (b) is correct: Benzene-(4), Acetaldehyde-(2), and Chloroform-(1).

Step-by-step solution

Understand the Options

List 1 contains chemical compounds that need to be matched with characteristics or reactions listed in List 2. We need to match each item in List 1 with one item from List 2.

Analyze 'Benzene'

Benzene is a classic example of an aromatic hydrocarbon, characterized by its delocalized pi-electron cloud. Aromatic compounds follow Huckel's rule, which is given by the formula \(4n+2\) \(\pi\) -electrons. Thus, Benzene (in List 1, item 1) matches with item (4) from List 2.

Analyze 'Ethylene'

Ethylene is a simple alkene with no complex aromatic characteristics or usage in forming special compounds such as mustard gas. It can be involved in other reactions but doesn't match well with any given specific terms like silver mirror (which is related to Tollen's test for aldehydes and hence not for alkenes). Ethylene does not have an obvious match by the given information in this setup directly.

Analyze 'Acetaldehyde'

Acetaldehyde is an aldehyde that undergoes Tollen's test, producing a silver mirror when reacted with Tollen's reagent. Thus, Acetaldehyde (in List 1, item 3) matches with item (2) Silver mirror from List 2.

Analyze 'Chloroform'

Chloroform is involved in the synthesis of dangerous compounds like phosgene or mustard gas when reacting under specific conditions. Chloroform traditionally doesn't form silver mirror which is part of other compounds' reactions. So, without additional direct indication in List 2, Chloroform fits closer to item (1) Phosgene.

Review Your Matches

We matched Benzene to (4) \((4n+2)\) \(\pi\)\ -electrons, Acetaldehyde to (2) Silver mirror, and Chloroform to (1) Phosgene. Ethylene, although listed, didn't have a direct match but leaning insights were needed due to incomplete direct references.

Choose the Best Answer

Based on our matches: Benzene-(4), Acetaldehyde-(2), and Chloroform-(1). The option that lists these correctly is option (b): \((4), (3), (2)\).

Key concepts

Aromatic Hydrocarbons

Aromatic hydrocarbons are fascinating chemical compounds primarily distinguished by their unique ring-like molecular structure. A classic example is Benzene, recognized by its six carbon atoms arranged in a hexagonal ring. What sets aromatic hydrocarbons apart from other hydrocarbons is the stability derived from electron delocalization within the carbon ring.
One of the defining characteristics of these compounds is they follow Huckel's rule, which provides insight into their stability and aromatic nature. This stability allows benzene and similar compounds to engage in various chemical reactions without disrupting their aromatic system. Some important traits of aromatic hydrocarbons include:

• High stability due to delocalized electrons
• Planar cyclic structures
• Ability to undergo electrophilic substitution reactions

Next time you encounter these compounds, remember that the aromaticity is not just about having a pleasant smell, which some may possess, but more about the special kind of stability provided by a specific configuration of electrons. This aromatic stability plays a critical role in many chemical reactions, allowing for complex combinations and products without losing their core aromatic character.

Huckel's Rule

Huckel's rule is a crucial principle in understanding aromaticity, particularly if a compound qualifies as an aromatic hydrocarbon. This rule is elegantly represented by the formula \(4n+2\) \(\pi\) electrons, where \(n\) can be any non-negative integer.
When you apply Huckel's rule, you can determine if a planar, cyclic molecule has aromatic properties. Its practicality is evident in explaining why benzene and other similar structures are stable. To break it down:

• The compound should have a planar, cyclic structure.
• It should possess conjugated \(\pi\) electrons that are free to move around.
• The number of these \(\pi\) electrons should follow \(4n+2\); for instance, in benzene, \(n=1\) leads to six electrons (which is 2,4,6, matching Huckel's rule).

Huckel's rule is more than just an equation; it's a window into predicting how certain compounds will behave during chemical reactions. It helps scientists and students alike understand the depths of chemical stability linked with electron configurations in aromatic compounds.

Tollen's Test

Tollen's test is an exciting reaction that involves observing the behavior of aldehydes with Tollen's reagent. This reagent contains silver nitrate and ammonia, producing a complex that reacts with aldehydes to generate a distinctive silver mirror on the inner walls of the container if the result is positive.
This test categorically distinguishes aldehydes from ketones, as only aldehydes will oxidize to form a carboxylic acid in the presence of Tollen's reagent, reducing \([Ag(NH_3)_2]^+\) to metallic silver:\[RCHO + 2[Ag(NH_3)_2]^+ + 3OH^- \rightarrow RCOO^- + 2Ag + 4NH_3 + 2H_2O\]Key points about Tollen's test include:

• It is used to detect aldehydes specifically.
• A positive result is marked by the formation of a shiny silver mirror.
• It provides a simple but effective way to differentiate aldehydes from other compounds.

In the context of this exercise, acetaldehyde reacts positively to Tollen's test, leading to a beautiful visual indication—a silver mirror—confirming its identity among the compounds.