Protection of carbonyl group is one of the most important protocol in multiple synthesis in organic, pharmaceutical and carbohyrate chemistry. There are a variety of reagents which have been used for this purpose. Acetals and ketals are multipurpose componds which have been used in organic chemistry. These functional groups can be used for identification, purification and protection of carbonyl groups. Other usful protecting groups are thioacetals and thioketals. In the first and second parts of this thesis Bu 4 N + HSO 4 - catalyst was used for synthesis of acetals, ketals, thioacetals and thioketals. In the third part of this thesis some alkyl iodides were synthesized from their corresponding alchols using Bu 4 N + HSO 4 - as a catalyst. These alkyl iodides are starting materials for carbon-carbon bond forming and synthesis of natural products.