NOVELTY - Preparation of 5- or 6-membered 1,3-heteroaryl alkylcarbonates (I) (containing nitrogen, phosphorus, arsenic or antimony and another heteroatom), free of corresponding carboxylates (III), involves reacting the parent heteroaromatic compound (V) and an alkylcarbonate (VI) in protic and/or polar solvent(s), the amount of solvent being 5-25 wt. % based on the overall reaction mixture.    USE - (I) are ionic compounds (i.e. ionic liquids or solids) showing useful properties such as absence of measurable vapor pressure, a wide liquidus range, good electrical conductivity and unusual solvation properties. They are useful e.g. as solvents for (in)organic syntheses (including transition metal catalyzed, biocatalyzed, phase transfer catalyzed, multiphase, photochemical, polymer synthesis and nanotechnological reactions); as extractants for liquid-liquid and liquid-gas extractions (e.g. for crude oil desulfurization, removing heavy metals from waste water or liquid membrane extraction); as electrolytes in fuel cells, batteries, capacitors, solar cells, sensors, electrochemistry, electroplating, electrochemical metal processing, elctrochemical or electroorganic syntheses or nanotechnology; as lubricants, thermal liquids, gels, organic synthesis reagents, replacements for volatile organic compounds, antistatic agents or liquid crystals; or in special analytical applications (e.g. gas chromatography, mass spectrometry or capillary zone electrophoresis).    ADVANTAGE - An efficient procedure is provided for preparing (I) free of contamination with (III).    DETAILED DESCRIPTION - Preparation of heteroaryl alkylcarbonates of formula (A)+(R2'OCOO)- (I), free of corresponding carboxylates of formula (E) (IIIc)-(IIIg), involves reacting a heteroaromatic compound of formula (F) (V) with an alkylcarbonate of formula R1'OCOOR2' (VI) in protic and/or polar solvent(s), the amount of solvent(s) being 5-25 (preferably 8-20) wt. % based on the overall reaction mixture.    (A)+ = 5- or 6-membered heteroaromatic cation of formula (IIa) or (IIb);    X, Z = N, P, As or Sb;    Y1 = O, S, Se, Te, N-R, P-R, As-R or Sb-R;    R, R1', R2' = alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl or heteroaryl (all optionally substituted (os)); and R may also be H;    or R1' + R2' = -CHRa-CHRb-, -CHRa-CH2-CHRb- or os 1,2-phenylene ((I)) in this case being a zwitterionic compound);    Ra, Rb = H or 1-6C alkyl;    R1 - R4 = H, halo, NO2, CN, ORc, SRc, NRcRd, CORc, COORc or CONRcRd; or (all os) alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl or heteroaryl;    Rc, Rd = H or (all os) alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl or heteroaryl;    or R + R1 or R + R2 (or in (IIb) also R2 + R3 or R3 + R4) = group (optionally interrupted by heteroatom(s) selected from O, S, N, NH or N(1-4C alkyl)) completing an os, unsaturated or aromatic ring;    provided that at least one of R1 - R4 = H;    (E) = group of formula (IIa; R2 or R3 replaced by COO-) or (IIb; R2, R3 or R4 replaced by COO-);    (F) = compound of formula (IIa) or (IIb) minus R1' and the positive charge.    An INDEPENDENT CLAIM is included for (I), free of (III), obtained by the process.