Question

The three isomeric tribromobenzenes, I, II, and III, when nitrated, form three, two, and one mononitrotribromobenzenes, respectively. Assign correct structures to I, II, and III.

Short answer

The structures of isomeric tribromobenzenes I, II, and III are 1,2,3-tribromobenzene, 1,2,4-tribromobenzene, and 1,3,5-tribromobenzene, respectively.

Step-by-step solution

Understand the concept of isomers and nitration

Isomers are compounds with the same molecular formula but different structural arrangements. In this case, tribromobenzenes will have the same molecular formula with different positions for bromine atoms. Nitration is a chemical process that introduces a nitro group into a molecule. For benzene ring, nitration will occur at positions ortho, meta or para relative to bromine atoms.

Derive possible isomers of tribromobenzenes

The three possible isomers for tribromobenzenes, based on the positions of bromine atoms, are 1,2,3-tribromobenzene (with bromine atoms at adjacent positions), 1,2,4-tribromobenzene (with a bromine atom at an ortho and para to another), and 1,3,5-tribromobenzene (bromine atoms occupy alternate positions).

Determine the possible nitration sites for each isomer and match with the information given

The 1,2,3-tribromobenzene can be nitrated at three different positions while 1,2,4-tribromobenzene can be nitrated at two positions, and 1,3,5-tribromobenzene can only be nitrated at one unique position. Matching this information with the given exercise, tribromobenzenes I, II, and III can be identified as 1,2,3-tribromobenzene, 1,2,4-tribromobenzene, and 1,3,5-tribromobenzene, respectively.

Establish and verify the structures of the isomers

Draw the structures of I, II, and III, and verify by cross-checking with nitration sites. Isomer I (1,2,3-tribromobenzene) has three possible nitration spots making it yield three products. Isomer II (1,2,4-tribromobenzene) has two possible nitration sites producing two products. Isomer III (1,3,5-tribromobenzene) has one unique nitration spot producing one product.

Key concepts

Chemical Isomers

In the world of chemistry, isomers play an essential role. They are compounds that share the same molecular formula but differ in the arrangement of their atoms. Even though they have the same number of each atom, their structures diverge, leading to different chemical properties.
For example, tribromobenzenes are all composed of the same types and numbers of atoms, specifically three bromine atoms attached to a benzene ring. However, the location of these bromine atoms around the benzene ring varies, creating different isomers.
It’s like dressing up differently using the same pieces of clothing! Each "outfit" or arrangement offers unique characteristics, impacting how the isomer reacts in various chemical processes.
Some common traits of chemical isomers include:

• Identical molecular formulas but different chemical structures
• Distinct chemical and physical properties
• Possible varied reactivity towards the same chemical reactions

Nitration Process

Nitration is a key chemical process utilized to introduce nitro groups (\(-NO_2\)) into organic compounds. It's a fundamental reaction in organic chemistry, especially when modifying aromatic compounds like benzene rings. How does it work? Primarily through a process called electrophilic aromatic substitution.
During nitration, a strong nitrating agent, often a mix of nitric acid (\(HNO_3\)) and sulfuric acid (\(H_2SO_4\)), replaces a hydrogen atom in an aromatic ring with a nitro group. This is achieved under controlled conditions to yield desired products.
Key points about the nitration process include:

• Important for synthesizing compounds with nitro functionalities
• Conducted under acidic conditions
• Relevant in producing pharmaceuticals, dyes, and explosives

For tribromobenzenes, the position of bromine atoms significantly influences where the nitro group will attach.

Tribromobenzene Structures

Tribromobenzene refers to a benzene molecule substituted with three bromine atoms. The structure is defined by the specific positions of these bromine atoms on the benzene ring. These positions create three distinct structural isomers: 1,2,3-, 1,2,4-, and 1,3,5-tribromobenzene.
Let's break them down:

• 1,2,3-tribromobenzene: Bromine atoms are consecutive on the ring, providing the highest symmetry among the isomers.
• 1,2,4-tribromobenzene: Offers a unique arrangement, with bromine atoms occupying two adjacent and one opposite position on the benzene ring.
• 1,3,5-tribromobenzene: This arrangement positions the bromine atoms alternately across the ring for another symmetric form.

Each structure impacts the compound's reactivity and possible nitration sites. Understanding these differences aids in predicting chemical behavior and product formation.

Nitration Sites

Nitration sites on a molecule refer to specific positions where a nitro group \((-NO_2)\) can attach during a nitration reaction. The exact locations depend significantly on other existing groups within the molecule.
In tribromobenzenes, bromine's positioning directs the possible nitration sites. The bromine atoms themselves can direct electrophiles, like the nitronium ion (\(NO_2^+\)), to specific positions on the benzene ring:

• Ortho: The postion immediately adjacent to a bromine.
• Meta: One carbon away from the bromine.
• Para: Directly opposite the bromine atom.

Understanding these concepts helps in determining how many mononitrotribromobenzene products can form, as seen in the given exercise. The structural arrangement of bromine influences the ease and number of possible nitration products.

Mononitrotribromobenzene

Mononitrotribromobenzenes are the resulting products after the nitration of tribromobenzene isomers. In simpler terms, they are tribromobenzene molecules that have been modified by adding one nitro group (\(-NO_2\)) through the nitration process.
The fascinating part is that each tribromobenzene isomer will yield a different number of mononitro products due to the specific nitration sites available.

• 1,2,3-tribromobenzene: Can form three different mononitro products due to its three unique sites available for nitration.
• 1,2,4-tribromobenzene: Produces two variations based on its two available sites for nitration.
• 1,3,5-tribromobenzene: Can only produce one mononitro compound owing to its one distinct nitration site.

These variations in product formation perfectly illustrate how structural isomerism influences chemical reactivity, helping chemists predict and control chemical reactions efficiently.