Alcohols Phenols And Ethers

To solve this question, we need to identify what PCC (Pyridinium Chlorochromate) is and its composition. PCC is commonly used as an oxidizing agent in organic chemistry.

Let's analyze the given options:

1. K₂Cr₂O₇ + Pyridine: This option refers to potassium dichromate mixed with pyridine. It is not known as PCC.
2. CrO₃ + CHCl₃: This represents chromium trioxide mixed with chloroform. It is not related to PCC.
3. CrO₃ + H₂SO₄: This combination results in chromic acid, which is a different oxidizing agent, not PCC.
4. A complex of chromium trioxide with pyridine + HCl: This is the correct description of PCC. It is formed when chromium trioxide is reacted with pyridine and hydrochloric acid, resulting in the formation of pyridinium chlorochromate (PCC).

Thus, the correct answer is that PCC is a complex of chromium trioxide with pyridine + HCl. This complex is represented by the chemical formula [C_5H_5NH]CrO_3Cl .

PCC is widely used because it can oxidize primary alcohols to aldehydes without further oxidizing them to carboxylic acids, making it a selective oxidizing agent in organic synthesis.

To determine which monohydric alcohol is involved, let's analyze the problem step by step.

1. The reaction given is between a monohydric alcohol and ethyl magnesium iodide, leading to the release of ethane. This reaction indicates the alcohol is a primary alcohol because only primary alcohols release ethane when reacted with Grignard reagents like ethyl magnesium iodide.
2. The release of ethane (C₂H₆) at STP is provided as 2240 cm³. At STP, 1 mole of any gas occupies 22400 cm³. Thus, the moles of ethane released can be calculated as:
3. This reaction implies that 0.1 mol of alcohol reacted, because each mole of alcohol will produce one mole of C₂H₆.
4. The molar mass of the alcohol can be determined using the weight of alcohol that reacted, which is 8.8 g. Using the formula:
5. From the options given, we identify which alcohol has a molecular weight of approximately 88 g/mol. Option '2,2-Dimethylpropan-1-ol' (C₅H₁₂O) has the molar mass:
6. Furthermore, the alcohol forms a carbonyl compound that answers Tollen’s test. Tollen's test is used to identify aldehydes. Oxidizing 2,2-Dimethylpropan-1-ol gives an aldehyde, which confirms it is the correct alcohol.
7. Thus, the correct answer is 2,2-Dimethylpropan-1-ol.

The problem deals with the dehydration of a tertiary alcohol under acidic conditions to form an alkene. Here is the step-by-step reasoning to identify the correct product and its IUPAC name:

1. The given alcohol is a tertiary alcohol with the molecular formula C_4H_{10}O . The most common tertiary alcohol with this formula is 2-methyl-2-propanol, also known as t-butanol.
2. When t-butanol is treated with 20% phosphoric acid (H_3PO_4) at 358 K, it undergoes dehydration. Dehydration involves the removal of a water molecule, resulting in the formation of an alkene.
3. Tertiary alcohols dehydrate to form alkenes via an E1 elimination mechanism, which proceeds through the formation of a carbocation intermediate. In this case, the carbocation is formed at the 2-position, leading to a more stable tertiary carbocation.
4. The IUPAC name for this compound, which is the major product of the reaction, is 2-Methylpropene.
5. Let's evaluate the other options:
   • But-1-ene: It requires deprotonation from the terminal carbon, which is less favorable.
   • But-2-ene: Not formed as it would require rearrangement that is not favorable given the carbocation stability.
   • Cyclobutane: No cyclization occurs given the reaction conditions and structure of the alcohol.
6. Therefore, the correct answer is 2-Methylpropene, which matches the reaction mechanism and expected outcome.