Consider the following statements.
I.The canonical forms have no real existence.
II. The molecule does not exist for a certain fraction of time in one canonical form and for other fractions of time in other canonical forms.
III. There is no such equilibrium between the canonical forms as we have between tautomerism.
IV. The molecule as such has a single structure which is the resonance hybrid of the canonical forms and which cannot as such be depicted by a single Lewis structure.
Which of the above are correct ? Choose the correct option.

Options

A. I and II
B. III and IV
C. II and III
D. I,II,III and IV

Answer

To solve the question regarding the correctness of the given statements about canonical forms and resonance structures, let’s analyze each statement step by step.

### Step 1: Analyze Statement I
**Statement I:** The canonical forms have no real existence.

**Explanation:** Canonical forms (or resonance structures) are hypothetical constructs used to represent the delocalization of electrons in a molecule. They do not exist as individual entities; rather, the actual molecule is a resonance hybrid of these forms. Therefore, this statement is **correct**.

### Step 2: Analyze Statement II
**Statement II:** The molecule does not exist for a certain fraction of time in one canonical form and for other fractions of time in other canonical forms.

**Explanation:** The molecule does not oscillate between different canonical forms over time. Instead, it exists as a resonance hybrid, which means it has characteristics of all the canonical forms simultaneously. Thus, this statement is also **correct**.

### Step 3: Analyze Statement III
**Statement III:** There is no such equilibrium between the canonical forms as we have between tautomerism.

**Explanation:** Tautomerism involves a dynamic equilibrium between two forms (like keto and enol forms), where each form can interconvert. In contrast, canonical forms do not exist in equilibrium; they are simply representations of the same molecule. Therefore, this statement is **correct**.

### Step 4: Analyze Statement IV
**Statement IV:** The molecule as such has a single structure which is the resonance hybrid of the canonical forms and which cannot as such be depicted by a single Lewis structure.

**Explanation:** The resonance hybrid is indeed the actual structure of the molecule, which cannot be accurately represented by any single Lewis structure. This statement is also **correct**.

### Conclusion
Since all four statements are correct, the answer to the question is that **all statements (I, II, III, and IV) are correct**.

### Final Answer
The correct option is **all of the above statements are correct**.

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