WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
29.12 - Aldehydes, whether or not with other oxygen function; cyclic polymers of aldehydes; paraformaldehyde. - Acyclic aldehydes without other oxygen function : 29 12.11 - - Methanal (formaldehyde) 2912.12 - - Ethanal (acetaldehyde) 2912.19 - - Other - Cyclic aldehydes without other oxygen function : 2912.21 2912.29 - - Benzaldehyde - - Other - Aldehyde-alcohols, aldehyde-ethers, aldehyde-phenols and aldehydes with other oxygen function : - - Vanillin (4-hydroxy-3-methoxybenzaldehyde) 29 12.42 - - Ethylvanillin (3-ethoxy-4-hydroxybenzaldehyde) 2912.41 - - Other 2912.50 - Cyclic polymers of aldehydes 2912.49 2912.60 - Paraformaldehyde These are compounds formed by oxidising primary alcohols; they contain the characteristic group : The are generally colourless liquids with a strong, penetrating odour; many aromatic aldehydes reachy oxldise on contact with iur, being converted lnto acids. The term " aldehydes, with other oxy en function " means aldehydes which contain also one or more of the oxygen functions referre to in previous sub-chapters (alcohol, phenol, ether, etc., functions). i (A) ALDEHYDES (I) Saturated acyclic aldehydes. (I) Methanal (formaldehyde) (HCHO . Obtained b catalytic oxidation of methanol. Colourless gas with a penetrating o our, highly so uble in water. Its aqueous solutions at about 40 % are known as formalin or formol, a colourless liquid urlth a penetrating and suffocating odour. These solutions may contain methanol as a stabiliser. r d Methanal has many applications; in organic synthesis (dyestuffs, explosives, pharmaceutical products, synthetic tanning agents, plastics, etc.), as an antiseptic, deodorant and reducing agent. (2) Ethanal (acetaldehyde) (CH3CHO). Obtained by oxidation of ethanol or from acetylene. Mobile, colourless liquid with a pungent, fruity odour; caustic; very volatile, inflammable; miscible with water, alcohol and ether. Used in organic synthesis to make plastics, varnishes, or iu medicine as an antiseptic. r (3) Butanal (butyraldehyde, normal isomer) CH3CH2CH2CHO).Colourless liquid, miscible with water, alcohol and ether; used or the preparation of plastics, perfumes and accelerators for vulcanising rubber. (4) Heptanal (heptaldeh de, oenanthol) (CH3(CH&CHO). Obtained by distilling castor oil; a colourless liqui with a penetrating odour. LI 's k (5) Octanal (caprylaldeh de (CSH160);nonanal elar onaldehyde (C9HLBO);decanal capraldehyde) (Clol&O\; undecanal (undecyic adehyde) (f.3 lIHuO); dodecanal [lauraldehyde) (CIZHxO),etC. These are wed as raw materials in the perfimery industry. (11) Unsaturated acyclic aldehydes. r (1) Propenal (acrylaldeh de, acraldehyde, acrolein) CH2=CHCHO). Formed when fatty matter is burned; a iquid with a characteristic itter and irritating odour; used in organic synthesis. b (2) 2-Butenal (crotonaldehyde) (CH3CH=CHCHO). Found in the first distillation products of crude alcohol; a colourless liquid with a penetrating odour. (3) Citral. Li uid with an agreeable odour, found in essential oil of tangerine, of citron, of lemons an ,more especially, in lemon grass oil. (4) Citronellaldehyde. Found in citron oil. (111) Cyclanic, cyclenic and cycloterpenic aldehydes. (1) Phellandral or tetrahydrocuminaldehyde. Found in fennel and eucalyptus oils. (2) Cyclocitrals A and B. Obtained fiom citral. (3) Perillaldehyde. Found in essential oils of the Perilla mankinensis. (4) Safranal. (IV)Aromatic aldehydes. (1) Benzaldehyde C6H5CHO).Highly refractive, colourless liquid with a characteristic odour of bitter a monds; used in organic synthesis, in medicine, etc. \ (2) Cinnamaldehyde (C6H5CH=CHCHO).Oily yellowish liquid with a strong odour of cinnamon; used in perfumery. (5) Phenylacetaldehyde (C6H5CH2CHO).Liquid with a pronounced odour of hyacinths; used in perfumery. (B) ALDEHYDE-ALCOHOLS, ALDEHYDE-ETHERS, ALDEHYDE-PHENOLS AND ALDEHYDES WITH OTHER OXYGEN FUNCTION Aldehyde-alcohohols are compounds which contain both the aldehyde function and the alcohol function. Aldehyde-ethers are ethers which contain also the aldehyde group (-CHO). Aldehyde henols are compounds which contain both the phenolic hydroxyl group (C6H50H) and the a1 ehyde group (-CHO). I' The most important aldehyde-alcohols, aldehyde-phenols and aldehyde-ethers are : (I) Aldol (CH3CH(OH)CH2CHO).Obtained by aldol condensation of acetaldehyde; colourless liquid which, when lefi undisturbed, polymerises to a crystalline mass (paraldol). Used in organic synthesis, for the manufacture of plastics, and in the flotation of ores. (2) Hydroxycitronellaldehyde (C10H~002)Colourless, slightly syrupy liquid with a very pronounced odour of Iily of the valley; used as a fixative in perfumery. (3) Glycollaldehyde (HOCH2CHO). Crystallises in colourless crystals. (4) Vanillin (4-hydroxy-3-mcthoxybenzaldehyde). The methyl ether of 3,4-dihydroxybcnzaldehyde (protocatechualdchyde); found in vanilla. Brilliant needles or crystalline white powder. (5) Ethylvanillin (3-ethoxy-4-hydroxybenzaldehyde).Fine white crystals. (6) Salicylaldehyde (o-h droxybenzaldehyde) (BOC6&CHO). Colourless oily li uid with a characteristic odour o bitter almonds; used for the manufacture of synthetic pe&es. P (7) 3,4-Dihydroxybenzaldehyde colourless crystals. (protocatechualdehyde) ((HO)2C6H3CHO). Brilliant (8) Anisaldehyde (CH30C6&CHO) (p-methoxybenzaldehyde). Found in aniseed and fenneI oils; colourless liquid. Used in perfumery under the name of (aubepine)". "hawthorn essence (C) CYCLIC POLYMERS OF ALDEHYDES (1) Trioxan (trioxymethylene). A solid polymer of formaldehyde; white crystalline substance, soluble in water, alcohol or ether. (2) Paraldeh de. A olyrner of ethanal; colourless liquid with an a reeable ether-like odour, highly in ammab e. Used in organic synthesis, as a soporific an disinfectant in medicine, etc. 'f l P (3) Metaldehyde. Also a polymer of ethanal; crystalline white powder, insoluble in water. This heading covers only metaldehyde in the form of crystals or powders. Metaldehyde put up in forms (for example, tablets, sticks or similar forms) for use as fuels is excluded (heading 36.06) (see Note 2 (a) to Chapter 36). (D) PARAFORMALDEHYDE This olymer (HO(CH20),H) is obtained by A so id, white, fl or powdered substance used to prepare p astics, waterproof glues disinfectant and a preserving agent. P "r solutions of formaldeh de. odour of formaldeh de. t is products, and a so as a r P This heading excludes aldeh de bisulpbite compounds which are classified as sulphonated derivatives of alcohols (headings 29.05 to ib.il). 29,13 -Halogenated, sulphonated, nitrated or nitrosated derivatives of products of heading 29.12. These are derived fkom aldehydes by r lacing one or more of the hydrogen atoms (other than a hydro en in the aldehyde group by one or more halogens, sul ho p u p s nitm groups (-N02) or nitroso groups (-NO) or by any combination thereo! SO^^), FCHO) The most important is chloral (trichloroacetaldehyde) (C13CCHO); anhydrous, mobile, colourless liquxd with a penetrating odour; a hypnotic. This heading excludes chloral hydrate (C13CCH(OH)2) (2,2,2-trichloroethane-1,l-diol)which falls in heading 29.05. This headin also excludes aldeh debisul hite compounds which are classified as sulphonated derivatives o f alcohols (headings 29.& to 2 9 . 9 ) . Sub-chapter VI KETONE-FUNCTION COMPOUNDS AND QUINONE-FUNCTION COMPOUNDS
1.- Except where the context otherwise requires, the headings of this Chapter apply only to : (a) Separate chemically defined organic compounds, whether or not containing impurities; (b) Mixtures of two or more isomers of the same organic compound (whether or not containing impurities), except mixtures of acyclic hydrocarbon isomers (other than stereoisomers), whether or not saturated (Chapter 27); (c) The products of headings 29.36 to 29.39 or the sugar ethers, sugar acetals and sugar esters, and their salts, of heading 29.40, or the products of heading 29.41, whether or not chemically defined; (d) The products mentioned in (a), (b) or (c) above dissolved in water; (e) The products mentioned in (a), (b) or (c) above dissolved in other solvents provided that the solution constitutes a normal and necessary method of putting up these products adopted solely for reasons of safety or for transport and that the solvent does not render the product particularly suitable for specific use rather than for general use; (f) The products mentioned in (a), (b), (c), (d) or (e) above with an added stabiliser (including an anti- caking agent) necessary for their preservation or transport; (g) The products mentioned in (a), (b), (c), (d), (e) or (f) above with an added anti-dusting agent or a colouring or odoriferous substance or an emetic added to facilitate their identification or for safety reasons, provided that the additions do not render the product particularly suitable for specific use rather than for general use; (h) The following products, diluted to standard strengths, for the production of azo dyes : diazonium salts, couplers used for these salts and diazotisable amines and their salts. 2.- This Chapter does not cover : (a) Goods of heading 15.04 or crude glycerol of heading 15.20; (b) Ethyl alcohol (heading 22.07 or 22.08); (c) Methane or propane (heading 27.11); (d) The compounds of carbon mentioned in Note 2 to Chapter 28; (e) Immunological products of heading 30.02; (f) Urea (heading 31.02 or 31.05); (g) Colouring matter of vegetable or animal origin (heading 32.03), synthetic organic colouring matter, synthetic organic products of a kind used as fluorescent brightening agents or as luminophores (heading 32.04) or dyes or other colouring matter put up in forms or packings for retail sale (heading 32.12); (h) Enzymes (heading 35.07); (ij) Metaldehyde, hexamethylenetetramine or similar substances, put up in forms (for example, tablets, sticks or similar forms) for use as fuels, or liquid or liquefied-gas fuels in containers of a kind used for filling or refilling cigarette or similar lighters and of a capacity not exceeding 300 cm3 (heading 36.06); (k) Products put up as charges for fire-extinguishers or put up in fire-extinguishing grenades, of heading 38.13; ink removers put up in packings for retail sale, of heading 38.24; or (l) Optical elements, for example, of ethylenediamine tartrate (heading 90.01). 3.- Goods which could be included in two or more of the headings of this Chapter are to be classified in that one of those headings which occurs last in numerical order. 4.- In headings 29.04 to 29.06, 29.08 to 29.11 and 29.13 to 29.20, any reference to halogenated, sulphonated, nitrated or nitrosated derivatives includes a reference to compound derivatives, such as sulphohalogenated, nitrohalogenated, nitrosulphonated or nitrosulphohalogenated derivatives. Nitro or nitroso groups are not to be taken as “nitrogen-functions” for the purposes of heading 29.29. For the purposes of headings 29.11, 29.12, 29.14, 29.18 and 29.22, “oxygen function”, the characteristic organic oxygen-containing group of those respective headings, is restricted to the oxygen-functions referred to in headings 29.05 to 29.20.