Aldehyde
Of all aldehydes, formaldehyde is produced the most. About 6 million tons per year are made.  It is mainly used to make resins when mixed with urea, melamine, and phenol. Bakelite is made like this.   Another commonly made aldehyde is butyraldehyde. 2 and a half million tons per year are made. A lot of acetaldehyde once was once made, but much less is made today.  This is because chemicals that used to be made from acetaldehyde are now made in other ways.