There is provided a fluorine-containing ether compound represented by the following formula. R.sup.1R.sup.2CH.sub.2R.sup.3CH.sub.2OCH.sub.2CH(OH)CH.sub.2OCH.sub.2R.sup.3CH.sub.2R.sup.4R.sup.5 (in the formula, R.sup.3 represents a perfluoropolyether chain; R.sup.2 and R.sup.4 represent a divalent linking group having a polar group and may be the same or different from each other; R.sup.1 and R.sup.5 represent a terminal group bonded to an oxygen atom of R.sup.2 or R.sup.4 and may be the same or different from each other; and at least one of R.sup.1 and R.sup.5 is an organic group having 1 to 8 carbon atoms and at least one of hydrogens included in the organic group is substituted by a cyano group).

A lubricant for a magnetic recording medium including an ionic liquid including a Bronsted acid and a Bronsted base that is primary amine as constituents of the ionic liquid, wherein the Bronsted acid includes a fluorine-containing chain, the Bronsted base includes a fluorine-containing chain that is a perfluoroalkyl chain or a perfluoropolyether chain, wherein the fluorine-containing chain in the Bronsted acid is a perfluoropolyether chain or the fluorine-containing chain in the Bronsted base is the perfluoropolyether chain, or the fluorine-containing chain in the Bronsted acid is the perfluoropolyether chain and the fluorine-containing chain in the Bronsted base is the perfluoropolyether chain, and a number average molecular weight of the fluorine-containing chain in the Bronsted acid is 1,500 or less.

A lubricant for a magnetic recording medium including an ionic liquid including a Bronsted acid and a Bronsted base that is primary amine as constituents of the ionic liquid, wherein the Bronsted acid includes a fluorine-containing chain, the Bronsted base includes a fluorine-containing chain that is a perfluoroalkyl chain or a perfluoropolyether chain, wherein the fluorine-containing chain in the Bronsted acid is a perfluoropolyether chain or the fluorine-containing chain in the Bronsted base is the perfluoropolyether chain, or the fluorine-containing chain in the Bronsted acid is the perfluoropolyether chain and the fluorine-containing chain in the Bronsted base is the perfluoropolyether chain, and a number average molecular weight of the fluorine-containing chain in the Bronsted acid is 1,500 or less.

A lubricant, which includes an ionic liquid including a conjugate base and a conjugate acid, wherein the conjugate acid is represented by General Formula (A) below, and wherein a pKa of an acid that is a source of the conjugate base in acetonitrile is 10 or less, ##STR00001##
where, in General Formula (A), R.sub.1, R.sub.2, and R.sub.3 are each independently a group including a hydrocarbon group, with the proviso that at least one of the hydrocarbon groups in R.sub.1, R.sub.2, and R.sub.3 is a straight-chain hydrocarbon group having 6 or greater carbon atoms.

A lubricant, which includes an ionic liquid including a conjugate base and a conjugate acid, wherein the conjugate acid is represented by General Formula (A) below, and wherein a pKa of an acid that is a source of the conjugate base in acetonitrile is 10 or less, ##STR00001##
where, in General Formula (A), R.sub.1, R.sub.2, and R.sub.3 are each independently a group including a hydrocarbon group, with the proviso that at least one of the hydrocarbon groups in R.sub.1, R.sub.2, and R.sub.3 is a straight-chain hydrocarbon group having 6 or greater carbon atoms.

A fluorine-containing ether compound represented by a formula (1) shown below.
R.sup.1(O(CH.sub.2).sub.a).sub.b-[A]-[B]OCH.sub.2R.sup.2CH.sub.2R.sup.3(1)
(In the formula (1), R.sup.1 is an alkyl group which may have a substituent, or an organic group having at least one double bond or triple bond. Further, a represents an integer of 2 to 4, and b is 0 or 1. [A] is represented by a formula (2): (OCH.sub.2CH(OH)CH.sub.2).sub.c (wherein c is 1 or 2). [B] is represented by a formula (3): (O(CH.sub.2).sub.eCH(OH)CH.sub.2).sub.d (wherein d is 0 or 1, and e represents an integer of 2 to 4). However, the sum of c in the formula (2) and d in the formula (3) is 2. R.sup.2 is a perfluoropolyether chain. R.sup.3 is represented by a formula (4): (OCH.sub.2CH(OH)CH.sub.2).sub.2OCH.sub.2(CH.sub.2).sub.fOH (wherein f represents an integer of 2 to 5).

A fluorine-containing ether compound represented by a formula (1) shown below.
R.sup.1(O(CH.sub.2).sub.a).sub.b-[A]-[B]OCH.sub.2R.sup.2CH.sub.2R.sup.3(1)
(In the formula (1), R.sup.1 is an alkyl group which may have a substituent, or an organic group having at least one double bond or triple bond. Further, a represents an integer of 2 to 4, and b is 0 or 1. [A] is represented by a formula (2): (OCH.sub.2CH(OH)CH.sub.2).sub.c (wherein c is 1 or 2). [B] is represented by a formula (3): (O(CH.sub.2).sub.eCH(OH)CH.sub.2).sub.d (wherein d is 0 or 1, and e represents an integer of 2 to 4). However, the sum of c in the formula (2) and d in the formula (3) is 2. R.sup.2 is a perfluoropolyether chain. R.sup.3 is represented by a formula (4): (OCH.sub.2CH(OH)CH.sub.2).sub.2OCH.sub.2(CH.sub.2).sub.fOH (wherein f represents an integer of 2 to 5).

A lubricating agent including an ionic liquid formed from a Bronsted acid (HX) and a Bronsted base (B), wherein the Bronsted base has a linear hydrocarbon group having 10 or more carbon atoms and the difference between the pKa value of the Bronsted acid in water and the pKa value of the Bronsted base in water is 12 or more.

A lubricating agent including an ionic liquid formed from a Bronsted acid (HX) and a Bronsted base (B), wherein the Bronsted base has a linear hydrocarbon group having 10 or more carbon atoms and the difference between the pKa value of the Bronsted acid in water and the pKa value of the Bronsted base in water is 12 or more.

Provided is a composition that contains a compound a) and at least one chemical entity b) dissolved in compound a). Compound a) has at least one sulfoxide functional group and/or one sulfone functional group, and at least one amide functional group. The composition is useful for a variety of applications, including manufacturing a film, a coating on a support, a hollow fiber, an artificial leather, a polymeric fiber, a membrane, a separator or an electrode for batteries, an electronic circuit or a sheath for the protection of electric cables.