Elimination reactions. Halogenoalkanes also undergo elimination reactions in the presence of sodium or potassium hydroxide. The 2-bromopropane has reacted to give an alkene - propene. Notice that a hydrogen atom has been removed from one of the end carbon atoms together with the bromine from the centre one.

Can Aqueous KOH Give Elimination Reaction?
Elimination reactions are common in organic chemistry and can occur with aqueous KOH under certain conditions. Here's a detailed explanation:

Conditions for Elimination Reaction:
- Aqueous KOH can promote elimination reactions in certain cases where a suitable substrate is present.
- The substrate should have a leaving group capable of forming a stable anion.
- The reaction conditions, such as temperature and concentration, can also influence the occurrence of an elimination reaction.

Mechanism of Elimination Reaction:
- In the presence of aqueous KOH, the base (OH-) can abstract a proton from the substrate to form an alkoxide ion.
- The alkoxide ion can then undergo elimination by losing a leaving group to form a double bond, resulting in the elimination product.

Types of Elimination Reactions:
- The most common types of elimination reactions are E1 and E2 mechanisms, which depend on the nature of the substrate and reaction conditions.
- E1 reactions proceed via a carbocation intermediate, while E2 reactions occur in a concerted manner.

Factors Influencing Elimination Reactions:
- The nature of the substrate, leaving group, and base can all affect the outcome of an elimination reaction.
- Steric hindrance and solvent effects can also play a role in determining the mechanism and product formation.
In conclusion, while aqueous KOH can facilitate elimination reactions under suitable conditions, it is essential to consider the specific factors that influence the reaction outcome. Understanding the mechanism and types of elimination reactions can help predict and control the product formation in organic synthesis.

No. An alkaline medium along with KOH is definitely required to carry out elimination (For instance, ethanol + KOH) . Now if you wonder why elimination product cannot be obtained in aq KOH (since KOH is a base as well), the reason is that even if KOH manages to extract a H+ from the reactant (as what happens in an elimination reaction), the aquous medium will resupply that H+ to the reactant.