WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
29.02 Cyclic hydrocarbons. - Cyclanes, cyclenes and cycloterpenes : 2902.1 1 -- 2902.19 - - Other 2902.20 - 2902.30 - Toluene Cyclohexane Benzene - Xylenes : 2902.41 - - o-Xylene 2902.42 2902.43 2902.44 2902.50 2902.60 2902.70 2902.90 - - m-Xylene - - p-Xylene - - Mixed xylene isomers - Styrene - Ethylbenzene - Curnene - Other Cyclic hydrocarbons are compounds containing on1 carbon and hydrogen which have at least one ring in thelr stmcture. They can be classified in tiree categories : (A) Cyclanes and cyclenes. (B) Cycloterpenes. (C) Aromatic hydrocarbons. (A) CYCLANES AND CYCLENES These are cyclic h drocarbons which correspond to the general formula C,H2, when they are (in which x may be 2, 4, 6, saturated monacycic cyclanes and to the general formula CnHZnnX etc.) when they are polycyclic cyclanes or when they are unsaturated (cyclenes). (1) The monocyclic cyclanes include the polyrnethylene and naphthene hydrocarbons found in certain petroleum oils; examples are : (a) Cyclopropane (C3H6) (gas). (b) Cyclobutane (C4H8) (gas). (c) Cyclopentane (CSH1O)(liquid). (d) Cyclohexane (C6H12)(liquid). (2) The polycyclic cyclanes include : (a) Decahydronaphthalene (CIJI18),a colourless liquid used as a solvent for paints and lacquers, for polishes, etc. (b) Bridge-linked compounds such as 1,4,4a,5,6,7,8,8a-octahydro-exo-1,4-endo-5,8dimethanonaphthalene (CLZHI6) fiom which the pesticide BEOD is derived. (c) Corn ounds with a "ca e" structure such as pentacyclo [ 5 . 2 . 1 . 0 ~ ~ ~ . 0 ~ ~ ~ . 0 ~ ~ ~ ( c l o g 2 )fiom which the ormula of dodecachlo~opentacyclo[5.2.1 .0z6.0'".0598j tzEE F is derived. (3) The cyclenes include : (a) Cyclobutene (C4H6) gas. (b) Cyclopentene (C5Hs), liquid. (c) Cyclohexene (C6HI0),liquid. (d) Cyclo-octatetraene (CsH8),liquid. (e) Azulene (CloHs),solid. This heading does not, however, include synthetic carotenes which fall in heading 32.04. (B) CYCLOTERPENES These hydrocarbons do not differ in general chemical structure from the cyclene group and have the general formula (CSH8),where n ma be 2 or more. They occur naturally in the vegetable kingdom as odoriferous, volatile liquids, or example : f (1) Pinene, a constituent of spirits of turpentine, pinewood oil, cinnamon oil, etc.; it is a colourless liquid. (2) Camphene, contained in nutmeg oil, petitgrain oil, etc. (3) Limonene, found in citrus fruit oils; dipentene, being the mixed optical isomers of lirnonene. Crude dipentene is excluded (heading 38.05). This heading excludes essential oils (heading 33.01), and m, wood or sulphate turpentine and other terpenic oils produced by the distillation or other treatment ogoniferous woods (heading 38.05). (C) AROMATIC HYDROCARBONS These compounds contain one or more ksed or unfused benzene rings, benzene being a h drocarbon composed of 6 atoms of carbon and 6 atoms of hydrogen, arranged in 6 groups of to form a hexagonal ring. (ZH) ( Hydrocarbons with only one benzene ring. These include benzene and its homologues. (a) Benzene (C6H6).&CUTS in coal gas, in some petroleum oils, and in the li id products of the dry distillation of numerous organic compounds rich in carbon Foal, lignite, etc.); also obtained synthetical1 . In the pure state, it is a colourless, moblle, refractive liquid, volatile and inflammab e, with an aromatic odour. It readily dissolves resins, fats, essential oils, rubber, etc. Numerous products can be obtained from benzene synthesis. r To fall in tlis heading, benzene must have a urity of 95 % or more by weight. Benzene of lower purity is excluded (heading 2&7). (b) Toluene methylbenzene) (C6&CH3). A benzene derivative in which one atom of hydrogen as been replaced by a methyl group. Obtained by distilling light coal tar oil, or by cyclisation of acyclic hydrocarbons. Colourless, mobile, refractive, inflammable liquid, with an aromatic odour similar to that of benzene. h To fall in this heading, toluene must have a purity of 95 % or more by weight. Toluene of lower purity is excluded (heading 27.07). (c) Xylene (dim& lbenzene) (C&&(CH&). A benzene derivative in which two atoms of hydrogen have i;een replaced by two meth 1 grou s. There are three isomers : o-xylene, m-xylene andpxylene. Xylene is a clear, & d i e liquid f w d in light coal tar oil. To fall in this heading, xylene must contain 95 % or more by weight of xylene isomers, all isomers being taken together. XyIene of lower purity is excluded (heading 27.07). (d) Other aromatic hydrocarbons of this grou are formed by a benzene ring and one or more side chains, open or closed; these inc ude : f' (1) Styrene (C6H5CH=CH2).A colourless, oily liquid used mainly in the preparation of plastics (polystyrene) and of synthetic rubber. (2) Eth Ibenzene (C6H5C2H5).A colourless inflammable, mobile liquid, contained in coa tar, normally manufactured from benzene and ethylene. (3) Cumene (C,SH~CH(CH~)~). A colourless liquid found in certain petroleum oils. Used mainly in the production of phenol, acetone or- methylstyrene or as a solvent. i! (4) p-Cymane (CH3C6WH(CH3)2. Found abundantly in several essential oils. Colourless liquid with an agreea le odour. Crudep-cymene is excluded (heading 38.05). (5) Tetrahydronaphthalene (tetralin) (CI0Hl2). Obtained by the catalytic hydrogenation of naphthalene. Colourless liquid, with a terpene-like odour, used as a solvent, etc. (11) Hydrocarbons with two or more unfused benzene rings; these include : (a) Biphenyl (C&CSH5). Sparkling white crystals with an agreeable odour; used in of the chlorinated derivatives lasticisers), as a coolant articular for the ether), and as a moderator in nuc ear reactors. alone or mixed P (Y (b) Diphenylmethane (C6H5CHZC&).A hydrocarbon with two benzene rings linked by a methylene group (CH2). Crystallises in colourless needles with a strong odour reminiscent of geraniums; used in organic synthesis. (c) Triphenylmethane (CH(C6H&). A methane with three atoms of hydrogen replaced by three benzene rings. (d) Te henyls. The mixed terphenyl isomers are used as coolants and as moderators in nuc ear reactors. 'P (111) Hydrocarbons with two or more benzene rings fused. (a) Naphthalene (C1a8).Results fiom the fusion of two benzene rings. It occurs in coal tar, in petroleum oils, in coal gas, in lignite tar, etc. It crystallises in fine white flakes, with a characteristic odour. To fa11 in this heading, naphthalene must have a c stallising point of 79.4 "C or more. Naphthalene of lower purity is excluded (heading 7.07). P (b) Phenanthrene (CI4HLO). Results fkom the hsion of three benzene rin s. One of the products of the distillation of coal tar; fine, colourless, fluorescent crysta s. k Phenanthrene falls here only when it is a separate chemically defined compound in the pure or commercially pure state. When crude, it is excluded (heading 27.07). (c) Anthracene (Cl4Hl0).Also results from the fusion of three benzene rin s, and is found in coal tar. Colourless crystals or yellowish powder, and is purple-blue uorescent. d To fall in this heading, anthracene must have a pwi of 90 % or more by weight. Anthracene of lower purity is excluded (heading 27.0x This group also includes the following hydrocarbons : (1) Acenaphthene. (2) Methylanthracenes. (3) Fluorene. (5) Pyrene. This heading excludes those dodecylbenzenes and those nonylnaphthalenes which are mixed alkylarenes (heading 38.17).
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.