which among the following statement is incorrect regarding the product formed when two molecules of HBr add to ethyne?

Options

A. IUPAC name is 1,1-dibromomethene
B. it is a geminal dihalide
C. It is a position isomer of 1,2-dibromomethene
D. It has a planer structure

Answer

To determine which statement is incorrect regarding the product formed when two molecules of HBr add to ethyne, we can follow these steps:

### Step 1: Understand the Reaction
When ethyne (C₂H₂) reacts with HBr, it undergoes an addition reaction. The first molecule of HBr adds across the triple bond, resulting in a vinyl bromide (bromoethene). The second molecule of HBr adds to the double bond, leading to the formation of a dibromide.

**Hint:** Consider the mechanism of electrophilic addition and how Markovnikov's rule applies.

### Step 2: Identify the Product
The addition of two HBr molecules to ethyne results in the formation of 1,1-dibromoethane. This is because both bromine atoms will attach to the same carbon atom due to Markovnikov's rule, which states that the more substituted carbon will receive the halogen.

**Hint:** Recall the concept of Markovnikov's rule and how it influences the addition of reagents to alkenes and alkynes.

### Step 3: Determine the IUPAC Name
The product formed, 1,1-dibromoethane, has two bromine atoms attached to the same carbon (the first carbon). Thus, the IUPAC name is indeed 1,1-dibromoethane.

**Hint:** Remember the naming conventions for organic compounds, especially for dihalides.

### Step 4: Analyze the Statements
1. **Statement 1:** "1,1-dibromo-methane" - This is incorrect because the product is 1,1-dibromoethane, not methane.
2. **Statement 2:** "It is a geminal dihalide" - This is correct as both bromine atoms are on the same carbon.
3. **Statement 3:** "It has a planar structure" - This is incorrect because the carbon atoms in 1,1-dibromoethane are sp³ hybridized, leading to a tetrahedral structure, not planar.
4. **Statement 4:** "It is a position isomer of 1,2-dibromo-ethane" - This is correct as they differ in the position of bromine atoms.

**Hint:** Carefully evaluate each statement based on the structure and properties of the product.

### Conclusion
The incorrect statements regarding the product formed when two molecules of HBr add to ethyne are:
- Statement 1: "1,1-dibromo-methane" (incorrect name)
- Statement 3: "It has a planar structure" (incorrect structure)

### Final Answer
The incorrect statements are Statement 1 and Statement 3.