The final major product of the reaction is :
`Ph - underset(underset(Ph)(|)) overset(overset(OH)(|))C - underset(underset(NH_2)(|))CH - CH_3 overset(NaNO_2 + "HCI") (to)`

Explanation

To solve the problem, we will analyze the reaction step by step.

### Step 1: Identify the Reactants
The reactant given is:
- A compound with a phenyl group (Ph), a hydroxyl group (OH), an amino group (NH2), and a methyl group (CH3).

### Step 2: Understand the Reaction Conditions
The reaction conditions provided are:
- Sodium nitrite (NaNO2) and hydrochloric acid (HCl). This combination is typically used for the diazotization of amines.

### Step 3: Diazotization Reaction
When the amino group (NH2) reacts with NaNO2 in the presence of HCl, it forms a diazonium salt. The amino group will be converted to a diazonium ion (Ar-N2+), and in this case, the NH2 group will be replaced by a diazonium group.

### Step 4: Elimination of Ammonia
The diazonium ion is unstable, and under certain conditions, it can lose nitrogen gas (N2) and ammonia (NH3). This results in the formation of a carbocation.

### Step 5: Rearrangement and Product Formation
The carbocation formed can rearrange or react with other groups present in the molecule. In this case, the phenyl group and the carbon chain will rearrange to stabilize the positive charge.

### Step 6: Final Product
After the rearrangement and elimination of H+, the final major product can be represented as:
- Ph-C(=O)-CH-CH3
This indicates that a carbonyl (C=O) group is now present, and the structure has been stabilized.

### Final Answer
The final major product of the reaction is:
- Ph-C(=O)-CH-CH3

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