Benzaldehyde is also called benzoic aldehyde. Benzaldehyde is an organic compound, and is synthetized by the way that the hydrogen of benzene is substituted by aldehyde. It is the most simple, and also the most commonly used industrial aromatic aldehyde. It is a Colorless or light yellow liquid at room temperature and has a special almond odor. Benzaldehyde is a compound that aldehyde is directly linked to the phenyl group, because it has a similar bitter almond flavor. Benzaldehyde widely exists in plant, especially in the Rosaceae plants. It is mainly in the form of glycosides in plant stem bark, leaves or seeds, such as amygdalin, bitter almond, cherry, laurel, peach. Benzaldehyde is naturally in bitter almond oil, patchouli oil, hyacinth oil, cananga oil. The compound is also in the nutlets and nuts, and exists in the form of Amygdalin, which is combination of glycosides. The chemical properties of Benzaldehyde is similar to that of aliphatic aldehydes, but It is also different. Benzaldehyde cannot reduce fehling reagent. When the reducing fat is used to reduce the benzaldehyde, the main products are benzene methanol, four substituted for the ortho - glycol and two - phenyl ethylene glycol. In the presence of potassium cyanide, two molecules of benzaldehyde form benzoin by acceptance the hydrogen atom. The substitution reaction in aromatic nucleus of benzaldehyde is mainly the meta-position product. For example, the main product is the m-nitrobenzaldehyde , when benzaldehyde is nitrated. Today, the benzaldehyde is prepared by different methods.