A schematic analysis of the reaction of the enantiomer with racemic mixture is shows below:
`{:(d,+,"d and l",rarr,(d)-(d)),("The(+)-form of",,"A racemic mixture of",,+),("chiral molecules",,"other molecules with",,(d)-(l)),(,,50%(d) and 50%(l),,):}`
The products (d-d) and (d-l) are clearly neither identical nor enantiomers (non-superimposable mirror images) as the diastereomers, stereoisomers that are not mirror images' . The formation of diasteromers allows the separation of enantiomers (called resolution) which is not easy as enantiomers have identical physical properties. One general with naturally occurring chiral molecule to form a pair of diastereomers. These can be separated easily as they have different physical properties. If the original chemical reaction can be reversed, the enantiomers can be isolated.
Which of the following is not true ?

Options

A. (a) Diastereomers have different melting points and solubilities in a given solvent.
B. (b) Diasteromers have similar chemical properties.
C. (c) Distereomers are optically active compounds with same or optisite sign of rotaion.
D. (d) Diastereomers differ in adsorption.

Explanation

To determine which statement is not true regarding diastereomers and enantiomers, we will analyze each statement based on the information provided in the question and the video transcript.

### Step-by-Step Solution:

1. **Understanding Diastereomers and Enantiomers**:
- Enantiomers are stereoisomers that are non-superimposable mirror images of each other.
- Diastereomers are stereoisomers that are not mirror images and have different physical properties.

2. **Analyzing the Statements**:
- **Statement 1**: "Diastereomers have different melting and solubility points and solubilities in a given solvent."
- This statement is true because diastereomers, having different physical properties, will exhibit different melting points and solubility characteristics.

- **Statement 2**: "Diastereomers have similar chemical properties."
- This statement is also true. While diastereomers differ in physical properties, they often exhibit similar chemical reactivity due to having the same functional groups.

- **Statement 3**: "Diastereomers are optically active compounds with the same or opposite sign of rotation."
- This statement is incorrect. Diastereomers can be optically active, but they do not necessarily have the same or opposite specific rotations. Each diastereomer can have a different optical activity, and they do not have to exhibit a direct relationship in their optical rotation.

- **Statement 4**: "Diastereomers differ in adsorption."
- This statement is true. Since adsorption is a physical property, and diastereomers have different physical properties, they will also differ in their adsorption characteristics.

3. **Conclusion**:
- The statement that is not true is **Statement 3**: "Diastereomers are optically active compounds with the same or opposite sign of rotation."

### Final Answer:
The statement that is not true is **Statement 3**.

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