Carboxylic acids are characterized by the presence in their structure of one or more carboxyl groups (–COOH), which bring to the molecule a proton donor character (acidic character). Carboxylic acids have the capability to form anions and salts (carboxylates). Thermal decomposition of organic acids with two or more COOH groups in the molecule may take place at a single carboxyl group or with simultaneous participation in the decomposition process of both groups. This chapter presents the pyrolysis of di- and polycarboxylic acids such as oxalic acid; malonic and malonic type acids; succinic and glutaric type acids; maleic, fumaric, and glutaconic acids; adipic and pimelic type acids; aromatic dicarboxylic acids; and polycarboxylic acids. Hydroxy acids are compounds containing in their structure both carboxyl and hydroxyl groups. Depending on the position of the two groups (OH and COOH), hydroxyl acids are classified as α-hydroxy acids (the COOH and OH attached on the same carbon), β-hydroxy acids, γ-hydroxy acids, etc. The chapter describes the pyrolysis of carboxylic acids with other additional functionalities or groups such as halogeno acids; cyclic ether acids; aldehyde acids and keto acids; lactonic acids; and acids with the carboxyl group attached to an aromatic heterocycle. The chapter explores the pyrolysis of organic acid salts that is utilized in organic synthesis as well as for the preparation of specific inorganic combinations such as oxides or even metals or superconducting materials.
This chapter discusses the pyrolysis of various derivatives of carboxylic acids. Typical reaction for the pyrolysis of esters that contain hydrogen at the β-carbon in the R2 group from the alcohol moiety forms an acid and an alkene. This reaction takes place by an Ei concerted mechanism, where the esters of alcohols that do not have a β-hydrogen in the alcohol moiety decompose differently under the influence of heat. In case of pyrolysis of methyl esters, the decomposition of methyl acetate takes place with the formation of H2, CH4, CO,H2O, and low levels of ethylene, acetic acid, acetaldehyde, formaldehyde, etc. The pyrolysis products of acetamide have the capability to react and the resulting compounds may undergo further pyrolytic decompositions. The amides of propionic acid, butyric acid, isobutyric acid, isovaleric acid, and caproic acid decompose around 400°C and generate nitriles. The decomposition of borates (orthoborates) of alcohols with β-hydrogens takes place with the formation of an alkene and boric acid. Pyrolysis of alcoxy ethyl borates generates mainly dioxane, acetals, and traces of vinyl ethers.
The chapter describes the pyrolysis of amines and imines. Primary amines can be considered as compounds derived from ammonia by the substitution of a hydrogen atom with an organic radical alkyl or aryl or as compounds resulting from the substitution of a hydrogen atom from an organic molecule with the group NH2. The chapter discusses pyrolysis of two types of primary amines known as aliphatic and aromatic. Secondary amines can be considered as compounds derived from ammonia by the replacement of two hydrogens with organic radicals and tertiary amines can be considered as derived from ammonia by the replacement of all three hydrogens with organic radicals. The chapter describes the pyrolysis of secondary and tertiary amines. Pyrolysis of amine salts and quaternary ammonium hydroxides is also discussed. Besides the amino groups (primary, secondary, tertiary, and quaternary), other functional groups can be present in organic molecules. The chapter presents the pyrolysis of organic compounds with amino and halogen groups and with amino and OH groups. The chapter also describes the pyrolysis of imines.
This chapter describes the pyrolysis of thiols, sulfides, and disulfides. This includes compounds such as α- and β-thiols, aromatic thiols such as benzene thiol, sulfides such as dibenzyl sulfide, etc. The formation of special compounds such as sulflower is also discussed.
This chapter describes the pyrolysis of aldehydes and ketones. Aldehydes are carbonyl compounds with the general formula R–CH=O, where R is a hydrocarbon radical. The chapter discusses the pyrolysis of several types of aldehydes such as formaldehyde, acetaldehyde, benzaldehyde, and other simple aldehydes. Ketones are carbonyl compounds with the general formula R–(CO)–R’, where R and R’ are hydrocarbon radicals. Ketones are important chemical compounds. They are present in nature and are synthesized for many applications. Ketones are used mainly as solvents and intermediates in chemical industry. Pyrolysis of ketones may occur in incinerators, in unintentional fires, and in some synthetic procedures such as the preparation of ketene. The chapter discusses pyrolysis of acetone. Pyrolysis of methyl ethyl ketone and diethyl ketone takes place similarly to that of acetone. The compounds generated include CO, H2, CH4, C2H4, C2H6, C2H2, and other short chain unsaturated hydrocarbons. Numerous compounds contain ketone groups in addition to other functional groups. These may include halogen, alcohol, ether, and other groups. The study of ketene pyrolysis is related particularly with the pyrolysis of acetone and with combustion of different fuels. Besides pyrolysis of ethenone (ketene), several studies on other ketenes and ketene dimers were performed. One of these studies evaluated thermal decomposition of dichloroketene. The replacement of the oxygen atom in the formula of an aldehyde or ketone with a sulfur atom leads to the formation of thioaldehydes and thioketones, respectively. The chapter also discusses the pyrolysis of thioaldehydes and thioketones.
