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Volumn 14, Issue 10, 2010, Pages 1037-1049

Use of the simple and extended grunwald-winstein equations in the correlation of the rates of solvolysis of highly hindered tertiary alkyl derivatives

Author keywords

[No Author keywords available]

Indexed keywords

AROMATIC COMPOUNDS; CARBON; CHLORINE COMPOUNDS; FREE ENERGY;

EID: 77953374045     PISSN: 13852728     EISSN: None     Source Type: Journal    
DOI: 10.2174/138527210791130505     Document Type: Article
Times cited : (15)

References (48)
  • 1
    • 33947441989 scopus 로고
    • The correlation of solvolysis rates
    • Grunwald, E.; Winstein, S. The correlation of solvolysis rates. J. Am. Chem. Soc., 1948, 70, 846-854.
    • (1948) J.Am.Chem.Soc , vol.70 , pp. 846-854
    • Grunwald, E.1    Winstein, S.2
  • 2
    • 44649161083 scopus 로고    scopus 로고
    • Sixty years of the Grunwald-Winstein equation: Development and recent applications
    • Kevill, D.N.; D'Souza, M.J. Sixty years of the Grunwald-Winstein equation: Development and recent applications. J. Chem. Res., 2008, 61-66.
    • (2008) J. Chem. Res , pp. 61-66
    • Kevill, D.N.1    D'Souza, M.J.2
  • 3
    • 0001350936 scopus 로고
    • The reactivity of bridgehead compounds of adamantane
    • Schleyer, P.V.R.; Nicholas, R.D. The reactivity of bridgehead compounds of adamantane. J. Am. Chem. Soc., 1961, 83, 2700-2707.
    • (1961) J. Am. Chem. Soc , vol.83 , pp. 2700-2707
    • Schleyer, P.V.R.1    Nicholas, R.D.2
  • 4
    • 33644610627 scopus 로고
    • Medium effects on the rates and mecha-nisms of solvolytic reactions
    • Bentley, T.W.; Schleyer, P.V.R. Medium effects on the rates and mecha-nisms of solvolytic reactions. Adv. Phys. Org. Chem., 1977, 14, 32-40.
    • (1977) Adv. Phys. Org. Chem , vol.14 , pp. 32-40
    • Bentley, T.W.1    Schleyer, P.V.R.2
  • 6
    • 33845553885 scopus 로고
    • The SN2-SN1 spectrum. 4. Mechanism for sol-volyses of tert-butyl chloride: A revised Y scale of solvent ionizing power ased on solvolyses of 1-adamantyl chloride
    • Bentley, T.W.; Carter, G.E. The SN2-SN1 spectrum. 4. Mechanism for sol-volyses of tert-butyl chloride: A revised Y scale of solvent ionizing power ased on solvolyses of 1-adamantyl chloride. J. Am. Chem. Soc., 1982, 104, 5741-5747.
    • (1982) J. Am. Chem. Soc , vol.104 , pp. 5741-5747
    • Bentley, T.W.1    Carter, G.E.2
  • 7
    • 0001254050 scopus 로고
    • Essentially solvent-independent rates of sol-volysis of the 1-adamantyldimethylsulfonium ion. Implications regarding nu-cleophilic assistance in solvolyses of tert-butyl derivatives and the NKL solvent nucleophilicity scale
    • Kevill, D.N.; Anderson, S.W. Essentially solvent-independent rates of sol-volysis of the 1-adamantyldimethylsulfonium ion. Implications regarding nu-cleophilic assistance in solvolyses of tert-butyl derivatives and the NKL solvent nucleophilicity scale. J. Am. Chem. Soc., 1986, 108, 1579-1585.
    • (1986) J. Am. Chem. Soc , vol.108 , pp. 1579-1585
    • Kevill, D.N.1    Anderson, S.W.2
  • 8
    • 37049080954 scopus 로고
    • Weakly nucleophilic leaving groups. Solvolyses of 1-adamantyl and t-butyl heptafluorobutyrates and trifluoroacetates
    • Bentley
    • Bentley, T.W.; Roberts, K. Weakly nucleophilic leaving groups. Solvolyses of 1-adamantyl and t-butyl heptafluorobutyrates and trifluoroacetates. J. Chem. Soc. Perkin II., 1989, 1055-1060.
    • (1989) J. Chem. Soc. Perkin II , pp. 1055-1060
    • Bentley, T.W.1    Roberts, K.2
  • 9
    • 33845377388 scopus 로고
    • Relative reactivity of bridgehead adamantyl and homoadamantyl substrates from solvolyses with heptafluoro-butyrate as a highly reactive carboxylate leaving group. Absence of SN2 character of solvolysis of tert-butyl derivatives
    • Fǎrcasciu, D.; Jähme, J.; Rüchardt, C. Relative reactivity of bridgehead adamantyl and homoadamantyl substrates from solvolyses with heptafluoro-butyrate as a highly reactive carboxylate leaving group. Absence of SN2 character of solvolysis of tert-butyl derivatives. J. Am. Chem. Soc., 1985, 107, 5717-5722.
    • (1985) J. Am. Chem. Soc , vol.107 , pp. 5717-5722
    • Fǎrcasciu, D.1    Jähme, J.2    Rüchardt, C.3
  • 10
    • 0035823833 scopus 로고    scopus 로고
    • Is the tert-butyl chloride solvolysis the most misunderstood reaction in organic chemistry? Evidence against nucleophilic solvent partici-pation in the tert-butyl chloride transition state and for increased hydrogen bond donation to the 1-adamantyl chloride solvolysis transition state
    • Gajewski, J.J. Is the tert-butyl chloride solvolysis the most misunderstood reaction in organic chemistry? Evidence against nucleophilic solvent partici-pation in the tert-butyl chloride transition state and for increased hydrogen bond donation to the 1-adamantyl chloride solvolysis transition state. J. Am. Chem. Soc., 2001, 123, 10877-10883.
    • (2001) J. Am. Chem. Soc , vol.123 , pp. 10877-10883
    • Gajewski, J.J.1
  • 11
    • 4644348155 scopus 로고    scopus 로고
    • Role of nucleophilic solvation and the mechanism of covalent bond heterolysis
    • Dvorko, G. F.; Ponomareva, E.A.; Ponomarev, M.E. Role of nucleophilic solvation and the mechanism of covalent bond heterolysis. J. Phys. Org.Chem., 2004, 17, 825-836.
    • (2004) J. Phys. Org.Chem , vol.17 , pp. 825-836
    • Dvorko, G.F.1    Ponomareva, E.A.2    Ponomarev, M.E.3
  • 12
    • 10044295086 scopus 로고    scopus 로고
    • Solvolysis model for 2-chloro-2-methyladamantane based on the linear solvation energy ap-proach
    • McManus, S.P.; Somani, S.; Harris, J.M.; McGill, R.A. A solvolysis model for 2-chloro-2-methyladamantane based on the linear solvation energy ap-proach. J. Org. Chem., 2004, 69, 8865-8873.
    • (2004) J. Org. Chem. , vol.69 , pp. 8865-8873
    • McManus, S.P.1    Somani, S.2    Harris, J.M.3    McGill, R.A.A.4
  • 13
    • 0000354711 scopus 로고
    • Nucleophilic participation in the solvolysis of the t-butyldimethylsulfonium ion
    • Kevill, D.N.; Kamil, W.A.; Anderson, S.W. Nucleophilic participation in the solvolysis of the t-butyldimethylsulfonium ion. Tetrahedron Lett., 1982, 23, 4635-4638.
    • (1982) Tetrahedron Lett , vol.23 , pp. 4635-4638
    • Kevill, D.N.1    Kamil, W.A.2    Anderson, S.W.3
  • 14
    • 33747144106 scopus 로고    scopus 로고
    • Correlations and predictions of solvent effects on reactivity: Some limitations of multi-parameter equations and comparisons with similarity models based on one solvent parameter
    • Bentley, T.W.; Garley, M.S. Correlations and predictions of solvent effects on reactivity: some limitations of multi-parameter equations and comparisons with similarity models based on one solvent parameter. J. Phys. Org. Chem., 2006, 19, 341-349.
    • (2006) J. Phys. Org. Chem , vol.19 , pp. 341-349
    • Bentley, T.W.1    Garley, M.S.2
  • 16
    • 33947460727 scopus 로고
    • Correlation of solvolysis rates. III. t-Butyl chloride in a wide range of solvent mixtures
    • Fainberg, A.H.; Winstein, S. Correlation of solvolysis rates. III. t-Butyl chloride in a wide range of solvent mixtures. J. Am. Chem. Soc., 1956, 78, 2770-2777.
    • (1956) J. Am. Chem. Soc , vol.78 , pp. 2770-2777
    • Fainberg, A.H.1    Winstein, S.2
  • 18
    • 33947456072 scopus 로고
    • The correlation of solvolyses rates and the classification of solvolysis reactions into mechanistic categories
    • Winstein, S.; Grunwald, E.; Jones, H.W. The correlation of solvolyses rates and the classification of solvolysis reactions into mechanistic categories. J. Am. Chem. Soc., 1951, 73, 2700-2707.
    • (1951) J. Am. Chem. Soc , vol.73 , pp. 2700-2707
    • Winstein, S.1    Grunwald, E.2    Jones, H.W.3
  • 19
    • 0002732089 scopus 로고    scopus 로고
    • Development and uses of scales of solvent nucleophilicity
    • Charton, M. Ed; JAI Press: Greenwich, CT
    • Kevill, D.N. Development and uses of scales of solvent nucleophilicity. In Advances in quantitative structure-property relationships, Charton, M. Ed; JAI Press: Greenwich, CT, 1996, Vol. 1, pp. 81-115.
    • (1996) Advances in Quantitative Structure-Property Relationships , vol.1 , pp. 81-115
    • Kevill, D.N.1
  • 20
    • 0001496673 scopus 로고
    • Correlation of solvolysis rates with three- and four-parameter relations. Scale of solvent nucleophilicities
    • Bentley, T.W.; Schadt, F.L.; Schleyer, P.V.R. Correlation of solvolysis rates with three- and four-parameter relations. Scale of solvent nucleophilicities. J. Am. Chem. Soc., 1972, 94, 992-995.
    • (1972) J. Am. Chem. Soc , vol.94 , pp. 992-995
    • Bentley, T.W.1    Schadt, F.L.2    Schleyer, P.V.R.3
  • 21
    • 33847797449 scopus 로고
    • The SN2-SN1 spectrum. 2. Quantitative treatments of nucleophilic solvent assistance. A scale of solvent nucleophilicities
    • Schadt, F.L.; Bentley, T.W.; Schleyer, P.V.R. The SN2-SN1 spectrum. 2. Quantitative treatments of nucleophilic solvent assistance. A scale of solvent nucleophilicities. J. Am. Chem. Soc., 1976, 98, 7667-7674.
    • (1976) J. Am. Chem. Soc , vol.98 , pp. 7667-7674
    • Schadt, F.L.1    Bentley, T.W.2    Schleyer, P.V.R.3
  • 22
    • 0000862017 scopus 로고
    • An improved scale of solvent nucleophilicitybased on the solvolysis of the S-methyldibenzothiophenium ion
    • Kevill, D.N.; Anderson, S.W. An improved scale of solvent nucleophilicitybased on the solvolysis of the S-methyldibenzothiophenium ion. J. Org.Chem., 1991, 56, 1845-1850.
    • (1991) J. Org.Chem , vol.56 , pp. 1845-1850
    • Kevill, D.N.1    Anderson, S.W.2
  • 23
    • 0000888651 scopus 로고
    • Correlation of solvolysis rates. VII. Neophyl chloride and bromide
    • Fainberg, A.H.; Winstein, S. Correlation of solvolysis rates. VII. Neophyl chloride and bromide. J. Am. Chem. Soc., 1957, 79, 1608-1612.
    • (1957) J. Am. Chem. Soc , vol.79 , pp. 1608-1612
    • Fainberg, A.H.1    Winstein, S.2
  • 24
    • 0001026937 scopus 로고
    • Correlation of solvolysis rates. VIII. Benzhydryl chloride and bromide. Comparison of mY and Swain's cor-relations
    • Winstein, S.; Fainberg, A.H.; Grunwald, E. Correlation of solvolysis rates. VIII. Benzhydryl chloride and bromide. Comparison of mY and Swain's cor-relations. J. Am. Chem. Soc., 1957, 79, 4146-4155.
    • (1957) J. Am. Chem. Soc , vol.79 , pp. 4146-4155
    • Winstein, S.1    Fainberg, A.H.2    Grunwald, E.3
  • 25
    • 84986533477 scopus 로고
    • Nucleophilic solvent intervention in benzylic solvolyses. The use of YBnX scales in Grunwald-Winstein type correlation analysis
    • Liu, K.-T. Nucleophilic solvent intervention in benzylic solvolyses. The use of YBnX scales in Grunwald-Winstein type correlation analysis. J. Chin.Chem. Soc., 1995, 42, 607-615.
    • (1995) J. Chin.Chem. Soc , vol.42 , pp. 607-615
    • Liu, K.-T.1
  • 26
    • 84987028523 scopus 로고
    • Concerning the development of scales of solvent ionizing power based on solvolyses of benzylic substrates
    • Kevill, D.N.; D'Souza, M.J. Concerning the development of scales of solvent ionizing power based on solvolyses of benzylic substrates. J. Phys. Org.Chem., 1992, 5, 287-294.
    • (1992) J. Phys. Org.Chem , vol.5 , pp. 287-294
    • Kevill, D.N.1    D'Souza, M.J.2
  • 27
    • 0000101046 scopus 로고
    • Solvolysis of the (p-Methoxybenzyl)dimethyl sulfonium ion. Development and use of a scale tocorrect for dispersion in Grunwald-Winstein plots
    • Kevill, D.N.; Ismail, N. H.J.; D'Souza, M.J. Solvolysis of the (p-Methoxybenzyl)dimethyl sulfonium ion. Development and use of a scale tocorrect for dispersion in Grunwald-Winstein plots. J. Org. Chem., 1994, 59, 6303-6312.
    • (1994) J. Org. Chem , vol.59 , pp. 6303-6312
    • Kevill, D.N.1    Ismail, N.H.J.2    D'Souza, M.J.3
  • 29
    • 0010732354 scopus 로고    scopus 로고
    • Application of the aromatic ring parameter (I) to solvolyses of -arylalkyl toluene-p-sulfonates
    • Kevill, D.N.; D'Souza, M.J. Application of the aromatic ring parameter (I) to solvolyses of -arylalkyl toluene-p-sulfonates. J. Chem. Soc. Perkin II, 1997, 257-263.
    • (1997) J. Chem. Soc. Perkin II , pp. 257-263
    • Kevill, D.N.1    D'Souza, M.J.2
  • 31
    • 0001095573 scopus 로고
    • The solvent effects on anchimerically assisted solvolyses. 2. Solvent effects in solvolyses of threo-2-aryl-1-methylpropyl p-toluenesulfonates
    • Fujio, M.; Saeki, Y.; Nakamoto, K.; Yatsugi, K.; Goto, M.; Kim, S.H.; Tsuji, Y.; Rappoport, Z.; Tsuno, Y. The solvent effects on anchimerically assisted solvolyses. 2. Solvent effects in solvolyses of threo-2-aryl-1-methylpropyl p-toluenesulfonates. Bull. Chem., Soc. Jpn., 1995, 68, 2603-2617.
    • (1995) Bull. Chem., Soc. Jpn , vol.68 , pp. 2603-2617
    • Fujio, M.1    Saeki, Y.2    Nakamoto, K.3    Yatsugi, K.4    Goto, M.5    Kim, S.H.6    Tsuji, Y.7    Rappoport, Z.8    Tsuno, Y.9
  • 32
    • 0013552799 scopus 로고    scopus 로고
    • Solvent effects on anchimerically assisted solvolyses. III. Solvent effects on the solvolyses of (1-arylcycloalkyl) methyl p-toluenesulfonates
    • Fujio, M.; Saeki, Y.; Nakamoto, K.; Kim, S.H.; Rappoport, Z.; Tsuno, Y.Solvent effects on anchimerically assisted solvolyses. III. Solvent effects on the solvolyses of (1-arylcycloalkyl) methyl p-toluenesulfonates Bull. Chem. Soc. Jpn., 1996, 69, 751-764.
    • (1996) Bull. Chem. Soc. Jpn , vol.69 , pp. 751-764
    • Fujio, M.1    Saeki, Y.2    Nakamoto, K.3    Kim, S.H.4    Rappoport, Z.5    Tsuno, Y.6
  • 33
    • 0001062722 scopus 로고    scopus 로고
    • B-strain and solvolytic reactivity revis-ited. Nucleophilic solvent participation and abnormal rate ratios for tertiary chloroalkanes
    • Liu, K.-T.; Hou, S.-J.; Tsao, M.-L. B-strain and solvolytic reactivity revis-ited. Nucleophilic solvent participation and abnormal rate ratios for tertiary chloroalkanes. J. Org. Chem., 1998, 63, 1360-1362.
    • (1998) J. Org. Chem , vol.63 , pp. 1360-1362
    • Liu, K.-T.1    Hou, S.-J.2    Tsao, M.-L.3
  • 34
    • 33947084937 scopus 로고
    • Solvent system ethanol-2,2,2-trifluoroethanol as a medium for solvolytic displacement
    • da Roza, D.A.; Andrews, L.J.; Keefer, R.M. Solvent system ethanol-2,2,2-trifluoroethanol as a medium for solvolytic displacement. J. Am. Chem. Soc.,1973, 95, 7003-7009.
    • (1973) J. Am. Chem. Soc , vol.95 , pp. 7003-7009
    • da Roza, D.A.1    Andrews, L.J.2    Keefer, R.M.3
  • 36
    • 0001575578 scopus 로고
    • Solvation effects adjacent to the reaction site. Differences in solvation between alkyl, alkenyl or alkynyl, and aryl groups in binary aqueous mixtures
    • Bentley
    • Bentley, T.W.; Dau-Schmidt, J.-P.; Llewellyn, G.; Mayr, H. Solvation effects adjacent to the reaction site. Differences in solvation between alkyl, alkenyl or alkynyl, and aryl groups in binary aqueous mixtures. J. Org. Chem., 1992, 57, 2387-2392.
    • (1992) J. Org. Chem , vol.57 , pp. 2387-2392
    • Bentley, T.W.1    Dau-Schmidt, J.-P.2    Llewellyn, G.3    Mayr, H.4
  • 37
    • 0003104087 scopus 로고
    • Additional YCl values and correlation of the specific rates of solvolysis of tert-butyl chloride in terms of NT and YCl scales
    • Kevill, D.N.; D'Souza, M.J. Additional YCl values and correlation of the specific rates of solvolysis of tert-butyl chloride in terms of NT and YCl scales. J. Chem. Res. Synop., 1993, 174-175.
    • (1993) J. Chem. Res. Synop , pp. 174-175
    • Kevill, D.N.1    D'Souza, M.J.2
  • 38
    • 53549099402 scopus 로고    scopus 로고
    • The influence of carbon-carbon multiple bonds on the solvolyses of tertiary alkyl halides: A Grunwald-Winstein analysis
    • Reis, M.C.; Elvas-Leitão, R.; Martins, F. The influence of carbon-carbon multiple bonds on the solvolyses of tertiary alkyl halides: A Grunwald-Winstein analysis. Int. J. Mol. Sci., 2008, 9, 1704-1716.
    • (2008) Int. J. Mol. Sci. , vol.9 , pp. 1704-1716
    • Reis, M.C.1    Elvas-Leitão, R.2    Martins, F.3
  • 39
    • 0001577016 scopus 로고    scopus 로고
    • Structural effects of the Grunwald-Winstein correlations in the solvolysis of some simple tertiary alkyl chlorides
    • Takeuchi, K.; Ohga, Y.; Ushino, T.; Takasuka, M. Structural effects of the Grunwald-Winstein correlations in the solvolysis of some simple tertiary alkyl chlorides. J. Phys. Org. Chem., 1997, 10, 717-724.
    • (1997) J. Phys. Org. Chem , vol.10 , pp. 717-724
    • Takeuchi, K.1    Ohga, Y.2    Ushino, T.3    Takasuka, M.4
  • 40
    • 0030807650 scopus 로고    scopus 로고
    • Grunwald Winstein relations in the solvolyses of highly congested simple secondary and tertiary alkyl systems. Evidence for the Brønsted base-type solvation in the standard 1- and 2-adamantyl systems
    • Takeuchi, K.; Ohga, Y.; Ushino, T.; Takasuka, M. Grunwald Winstein relations in the solvolyses of highly congested simple secondary and tertiary alkyl systems. Evidence for the Brønsted base-type solvation in the standard 1- and 2-adamantyl systems. J. Org. Chem., 1997, 62, 4904-4905.
    • (1997) J. Org. Chem , vol.62 , pp. 4904-4905
    • Takeuchi, K.1    Ohga, Y.2    Ushino, T.3    Takasuka, M.4
  • 41
    • 0001177196 scopus 로고
    • Chemical effects of steric strains. I. The effect of structure upon the hydrolysis of tertiary aliphatic chlorides
    • Brown, H.C.; Fletcher, R.S. Chemical effects of steric strains. I. The effect of structure upon the hydrolysis of tertiary aliphatic chlorides. J. Am. Chem. Soc., 1949, 71, 1845-1854.
    • (1949) J. Am. Chem. Soc , vol.71 , pp. 1845-1854
    • Brown, H.C.1    Fletcher, R.S.2
  • 42
    • 69549128039 scopus 로고    scopus 로고
    • Nucleophilic solvent participation in the solvolysis of tertiary bromoalkanes
    • Liu, K.-T.; Hou, S.-J.; Tsao, M.-L. Nucleophilic solvent participation in the solvolysis of tertiary bromoalkanes. J. Chin. Chem. Soc., 2009, 56, 425-430.
    • (2009) J. Chin. Chem. Soc , vol.56 , pp. 425-430
    • Liu, K.-T.1    Hou, S.-J.2    Tsao, M.-L.3
  • 43
    • 0009714294 scopus 로고
    • Correlation of solvolysis rates. VI. t-Butyl and -phenylethyl bromides
    • Fainberg, A.H.; Winstein, S. Correlation of solvolysis rates. VI. t-Butyl and -phenylethyl bromides. J. Am. Chem. Soc., 1957, 79, 1602-1608.
    • (1957) J. Am. Chem. Soc , vol.79 , pp. 1602-1608
    • Fainberg, A.H.1    Winstein, S.2
  • 44
    • 33947093270 scopus 로고
    • Application of the ethanol-trifluoroethanol method to solvolyses for which nucleophilic involvement is questioned
    • Harris, J.M.; Mount, D.L.; Smith, M.R.; Neal, W.C. Jr. Dukes, M.D. Raber, D.J. Application of the ethanol-trifluoroethanol method to solvolyses for which nucleophilic involvement is questioned. J. Am. Chem. Soc., 1978, 100, 8147-8156.
    • (1978) J. Am. Chem. Soc , vol.100 , pp. 8147-8156
    • Harris, J.M.1    Mount, D.L.2    Smith, M.R.3    Neal Jr., W.C.4    Dukes5    Raber, M.D.6
  • 45
    • 0001563975 scopus 로고
    • SN2 character of sol-volyses of tert-butyl halides and of trifluoroacetolyses of secondary alkyl sul-fonates
    • Bentley, T.W.; Bowen, C.T.; Parker, W.; Watt, C.I.F. SN2 character of sol-volyses of tert-butyl halides and of trifluoroacetolyses of secondary alkyl sul-fonates. J. Am. Chem. Soc., 1979, 101, 2486-2488.
    • (1979) J. Am. Chem. Soc , vol.101 , pp. 2486-2488
    • Bentley, T.W.1    Bowen, C.T.2    Parker, W.3    Watt, C.I.F.4
  • 46
    • 0032482488 scopus 로고    scopus 로고
    • Application of the aromatic ring parameter (I) to solvolyses of extremely crowded alkyl derivatives
    • Kevill, D.N.; D'Souza, M.J. Application of the aromatic ring parameter (I) to solvolyses of extremely crowded alkyl derivatives. Tetrahedron Lett., 1998, 39, 3973-3976.
    • (1998) Tetrahedron Lett , vol.39 , pp. 3973-3976
    • Kevill, D.N.1    D'Souza, M.J.2
  • 47
    • 0000001319 scopus 로고
    • Comparative study of the electrophilic properties of some protic solvents characterized by spectroscopic and kinetic solvent-sensitive standard process
    • Allard, B.; Casadevall, E. Comparative study of the electrophilic properties of some protic solvents characterized by spectroscopic and kinetic solvent-sensitive standard process. Nouv. J. Chim., 1985, 9, 565-568.
    • (1985) Nouv. J. Chim , vol.9 , pp. 565-568
    • Allard, B.1    Casadevall, E.2


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