« The aroma of pine trees is one that’s evocative of Christmas; one of the responsible molecules, alpha-pinene, has already been featured on the Chemistry Advent Calendar, but here we take a more detailed look at the chemical constituents of the aroma.
One of the most important contributors to the Christmas tree aroma is pinene.
Pinene is a compound which occurs naturally as two different isomers: Alpha-pinene, and beta-pinene. In most pine trees, alpha-pinene is the more abundant of the two, but both are commonly present in the resin of the trees. Turpentine is obtained from the resin of trees, primarily pines, so it’s not surprise that the odour of both alpha and beta-pinene is commonly described as turpentine-like – they are, in fact, the major constituents of the distilled oil.
Pinene belongs to a larger family of compounds known as terpenes. These are a huge range of organic compounds, commonly produced by plants. A range of different terpenes are released by various trees in forests, and these do more than simply providing the characteristic smells of the woods – scientists have discovered that the terpenes can react with some chemicals in the air to form small particles called aerosols. These aerosols can act as ‘seeds’ for clouds, allowing their formation from water vapour. Overall, the increased cloud cover can have a cooling effect.(…) »