Limonene and D-limonene are less toxic alternatives for mineral spirits. It contains methyl chavicol, anethole, anisaldehyde, limonene, pinene and linalool. Other compounds include perillaldehyde, limonene, linalool, beta-caryophyllene, menthol, and alpha-pinene. Citric flavours come from chemicals such as limonene and gamma-terpinene linalool. As fragrances, air freshener preparations often include terpenes such as limonene. The dominating monoterpenes were myrcene (67%) and limonene (16%). Spearmint oil also contains significant amounts of limonene, dihydrocarvone, and 1,8-cineol. Hydrazine and potassium hydroxide give limonene (6) via a Wolff-Kishner reduction. Other aromatic essential oils present are limonene, caryophyllene, and farnesene. The biosynthesis of carvone is by oxidation of limonene. These essential oils can include limonene and other straight solvents. A classic example is the cyclization of geranyl pyrophosphate to form limonene. This technology produces sulfur limonene polysulphide (proposed material) using sulfur and limonene. It oxidizes easily in moist air to produce carveol, carvone, and limonene oxide.