Final answer:
Out of the five statements provided by the student regarding SN1 and SN2 reactions, two statements (1 and 4) are true. Statement 1 is correct about primary alkyl halides favoring SN2, and statement 4 correctly notes that SN1 reactions lead to racemization.
Step-by-step explanation:
The student's question about SN1 and SN2 mechanisms in organic chemistry involves understanding the differences between these two types of nucleophilic substitution reactions and the conditions under which they occur. The truth of the statements provided by the student can be assessed based on the characteristics of the reactions mentioned.
- A primary alkyl halide will tend to react through an SN2 mechanism because there is little hindrance to backside attack and a primary carbocation is not very stable. This statement is true.
- 3-bromo-3-methylpentane will not undergo substitution through an SN2 mechanism due to significant steric hindrance from the methyl group at the tertiary carbon. This statement is false.
- If R-3-bromo-3-methylhexane is allowed to react with OH-, the product will not be a 50%/50% mixture of R-3-methyl-3-hexanol and S-3-methyl-3-hexanol due to steric hindrance affecting the SN2 mechanism, making this statement false.
- SN1 reactions lead to racemization of sterechemistry due to the planar carbocation intermediate. This statement is true.
- SN2 leads to inversion of sterechemistry due to the nucleophile attacking from the backside and the leaving group leaving, not racemization. This statement is false.
Therefore, out of the five given statements, only two are true (1 and 4).