7.8 Summary of the Features of Carbocation-Mediated …
215
7.8 Summary of the Features of Carbocation-Mediated
C–C Bond Formation in Methane Conversion
As discussed in this chapter, the key intermediate in carbocation-mediated methane
conversion is
+ CH 3 , which is essential for selective C–C bond formation. Thus, the
selective formation of
+ CH 3 is an important factor. Superacids and Ag
+ -exchanged
zeolites can selectively generate
+ CH 3 through the heterolytic dissociation of
methane C–H bonds. Carbenium ions such as
+ CH 3 are effective alkylating agents
and can react electrophilically with electron-rich molecules, except for ethylene
and benzene, to form non-C–C bonds (e.g., C–O and C–N bonds). Furthermore,
superacids and Ag-zeolites can produce carbenium ions through the heterolytic
C–H bond dissociation of alkanes other than CH 4 . This indicates that carbenium ion
generation methods should be extended to other molecules to develop new reactions,
i.e., catalysts that do not resemble superacids or Ag-zeolites should be designed to
promote the development of new reactions, catalyst characterization methods, and
chemical processes in methane conversion.
References
1. Olah GA, Schlosberg RH (1968) Chemistry in super acids. I. Hydrogen exchange and polycondensation of methane and alkanes in FSO 3 H-SbF 5 (“magic acid”) solution. Protonation
of alkanes and the intermediacy of CH 5
+ and related hydrocarbon ions. The high chemical
reactivity of “paraffins” in ionic solution reactions. J Am Chem Soc 90:2726–2727
2. Sommer J, Muller M, Loadi K (1982) Alkene-alkane alkylation catalyzed by the HF-TaF 5
acid system. Nou J Chim 6:3–6
3. Choudhary VR, Kinage AK, Choudhary TV (1997) Low-temperature nonoxidative activation
of methane over H-galloaluminosilicate (MFI) zeolite. Science 275:1286–1288
4. Baba T, Sawada H, Takahashi T, Abe M (2002) Chemisorption study of hydrogen and methane
by 1 H MAS NMR and conversion of methane in the presence of ethylene on Ag-Y zeolite.
Appl Catal A 231:55–63
5. Guo J, Lou H, Zhang X (2009) Energy-efficient coaromatization of methane and propane. J
Nat Gas Chem 18:260–272
6. Olah GA, Surya Prakash GK, Sommer J (1979) Superacids. Science 206:13–20
7. Olah GA, Surya Prakash GK, Goeppert A (2006) Fluorinated superacidic systems. Actulite
Chimique 301–302:68–72
8. Hammett LP, Deyrup AJ (1932) A series of simple basic indicators. I. The acidity functions
of mixtures of sulfuric and perchloric acids with water. J Am Chem Soc 54:2721–2739
9. Olah GA (1973) Carbocations and electrophilic reactions. Angew Chem Int Ed 12:173–211
10. Olah GA (1987) Electrophilic methane conversion. Acc Chem Res 20:422–428
11. Olah GA (2001) 100 years of carbocations and their significance in chemistry. J Org Chem
18:5943–5957
12. Bickel AF, Gaasbeek CJ, Hogeveen H, Oelderik JM, Platteeuw JC (1967) Chemistry and
spectroscopy in strong acidic solutions: reversible reaction between aliphatic carbenium ions
and hydrogen. Chem Commun 634–635
13. Hogeveen H, Bickel AF (1967) Chemistry and spectroscopy in strong acidic solutions:
Electrophilic substitution at alkane-carbon by protons. Chem Commun 635–636
215
7.8 Summary of the Features of Carbocation-Mediated
C–C Bond Formation in Methane Conversion
As discussed in this chapter, the key intermediate in carbocation-mediated methane
conversion is
+ CH 3 , which is essential for selective C–C bond formation. Thus, the
selective formation of
+ CH 3 is an important factor. Superacids and Ag
+ -exchanged
zeolites can selectively generate
+ CH 3 through the heterolytic dissociation of
methane C–H bonds. Carbenium ions such as
+ CH 3 are effective alkylating agents
and can react electrophilically with electron-rich molecules, except for ethylene
and benzene, to form non-C–C bonds (e.g., C–O and C–N bonds). Furthermore,
superacids and Ag-zeolites can produce carbenium ions through the heterolytic
C–H bond dissociation of alkanes other than CH 4 . This indicates that carbenium ion
generation methods should be extended to other molecules to develop new reactions,
i.e., catalysts that do not resemble superacids or Ag-zeolites should be designed to
promote the development of new reactions, catalyst characterization methods, and
chemical processes in methane conversion.
References
1. Olah GA, Schlosberg RH (1968) Chemistry in super acids. I. Hydrogen exchange and polycondensation of methane and alkanes in FSO 3 H-SbF 5 (“magic acid”) solution. Protonation
of alkanes and the intermediacy of CH 5
+ and related hydrocarbon ions. The high chemical
reactivity of “paraffins” in ionic solution reactions. J Am Chem Soc 90:2726–2727
2. Sommer J, Muller M, Loadi K (1982) Alkene-alkane alkylation catalyzed by the HF-TaF 5
acid system. Nou J Chim 6:3–6
3. Choudhary VR, Kinage AK, Choudhary TV (1997) Low-temperature nonoxidative activation
of methane over H-galloaluminosilicate (MFI) zeolite. Science 275:1286–1288
4. Baba T, Sawada H, Takahashi T, Abe M (2002) Chemisorption study of hydrogen and methane
by 1 H MAS NMR and conversion of methane in the presence of ethylene on Ag-Y zeolite.
Appl Catal A 231:55–63
5. Guo J, Lou H, Zhang X (2009) Energy-efficient coaromatization of methane and propane. J
Nat Gas Chem 18:260–272
6. Olah GA, Surya Prakash GK, Sommer J (1979) Superacids. Science 206:13–20
7. Olah GA, Surya Prakash GK, Goeppert A (2006) Fluorinated superacidic systems. Actulite
Chimique 301–302:68–72
8. Hammett LP, Deyrup AJ (1932) A series of simple basic indicators. I. The acidity functions
of mixtures of sulfuric and perchloric acids with water. J Am Chem Soc 54:2721–2739
9. Olah GA (1973) Carbocations and electrophilic reactions. Angew Chem Int Ed 12:173–211
10. Olah GA (1987) Electrophilic methane conversion. Acc Chem Res 20:422–428
11. Olah GA (2001) 100 years of carbocations and their significance in chemistry. J Org Chem
18:5943–5957
12. Bickel AF, Gaasbeek CJ, Hogeveen H, Oelderik JM, Platteeuw JC (1967) Chemistry and
spectroscopy in strong acidic solutions: reversible reaction between aliphatic carbenium ions
and hydrogen. Chem Commun 634–635
13. Hogeveen H, Bickel AF (1967) Chemistry and spectroscopy in strong acidic solutions:
Electrophilic substitution at alkane-carbon by protons. Chem Commun 635–636