Circumstances under which a purchase contract may be void:

1. Lack of capacity: If one or both parties to the contract are not legally capable of entering into a contract (e.g. minors, mentally incapacitated individuals), the contract may be void.

2. Fraud or misrepresentation: If one party intentionally deceives the other party or provides false information that influences their decision to enter into the contract, the contract may be void.

3. Illegal purpose: If the subject matter of the contract is illegal or against public policy, the contract may be void.

4. Mistake: If both parties make a mutual mistake about a material fact in the contract, the contract may be void.

5. Duress or undue influence: If one party is forced or coerced into entering into the contract, or if one party exerts undue influence over the other party, the contract may be void.

6. Impossibility: If circumstances arise that make it impossible to fulfill the terms of the contract, the contract may be void.

7. Lack of consideration: If one party fails to provide something of value in exchange for the other party's promise, the contract may be void.

8. Unconscionability: If the terms of the contract are so one-sided or unfair that they shock the conscience, the contract may be void.

Circumstances under which a Purchase Contract may be Void:

1. Duress or Undue Influence:
- If one party forced or coerced the other party into signing the contract under threats or undue pressure.

2. Fraud or Misrepresentation:
- If the buyer or seller knowingly provided false or misleading information that materially affected the other party's decision to enter into the contract.

3. Mistake:
- If a party entered into the contract based on a fundamental misunderstanding of its terms or the underlying facts.
- Mutual Mistake occurs when both parties are mistaken about a material fact.
- Unilateral Mistake occurs when only one party is mistaken about a material fact.

4. Illegal Purpose:
- If the contract involves an activity that is illegal or violates public policy.

5. Incapacity or Minors:
- If one party lacks the legal capacity to enter into a contract due to mental disability, intoxication, or being a minor.

6. Impossibility:
- If the contract becomes impossible to perform after it is signed due to factors beyond the parties' control.

7. Material Breach:
- If one party fails to fulfill a material term of the contract, which can void the contract in certain circumstances.

8. Public Policy:
- If the contract violates a fundamental principle of public policy or the law.

9. Statute of Frauds:
- In some cases, contracts for certain types of transactions must be in writing to be enforceable. If not, they may be void.

10. Waiver:
- If the parties mutually agree to waive certain terms or provisions of the contract, it can make the contract void in part.

Note: The specific rules and circumstances that determine whether a contract is void may vary depending on the jurisdiction and applicable laws.