Protic adds

Cyanohydrin formation is somewhat unusual because it is one of the few examples of the addition of a protic acid (H—Y) to a carbonyl group. As noted in the previous section, protic adds such as H20, HBr, HC1, and H2S04 don t normally yield carbonyl addition products because the equilibrium constants ate unfavorable. With HCN, however, the equilibrium favors the cyanohydrin adduct. 

A few methods exist for the formation of 1,2-cis isomers. Protic adds such as HC1 or AcOH in conjunction with thionyl chloride (SOCl2) furnish P-chlorides from... 

Yamada C, Sasaki K, Matsumura S, Toshima K (2007) Aryl C-glycosylation using an ionic liquid containing a protic add. Tetrahedron Lett 48 4223 227... 

All efforts to affect the requisite cyclization however proved futile. When rhodium acetate in benzene was used as a catalyst, C—H insertion of the resulting carbenoid occurred to furnish cyclobutanone 285, which was not isolated, but underwent ring opening to yield tetrahydro-P-carboline 286. The use of catalytic copper(I) triflate, protic add catalysis, and photolysis conditions were also explored, but the desired product was not obtained. 

Account for the following observations (a) Phosphorus forms a pentachloride, but nitrogen does not. (b) H3PO2 is a mono-protic add. (c) Phosphonium salts, such as PH4CI, can be formed under anhydrous conditions, but they can t he made in aqueous solution, (d) White phosphorus is more reactive than red phosphorus. 

Early-transition-metal amides are extremely reactive toward protic adds and are therefore useful precursors to a variety of M-X complexes (in which X is an anionic ligand less basic than an amide) by reaction of the amido complex with H-X (Equation 4.13). Common exchange processes that favor elimination of amine involve the reaction with alcohols, amides, amidines, and guanidines. However, weakly acidic hydrocarbons, such as cyclopentadiene derivatives, also react to form Cp complexes (Equation 4.14). ... 

Protic add An Arrhenius acid, or a Bronsted—Lowry acid. 

A Review of Strong Electroiytes 18-2 The Autoionization of Water 18-3 The pH and pOH Scales 18-4 Ionization Constants for Weak Monoprotic Adds and Bases 18-5 Poly protic Adds 18-6 Solvolysis... 

R. Yang, H. Zhang, D. Kirichenko, K Rogers, R. D., Ionic liquids via reaction of the zwitterionic l,3-dimethylimidazolium-2-carboxylate with protic adds. Overcoming synthetic limitations and establishing new halide free protocols for the formation of ILs. Green Chem, 2007, 9 (1), 90-98. 

CROP of oxiranes may be initiated by typical cationic initiators including strong protic adds (e.g., HOSO2CF3), Lewis adds (e.g., BF3 and its complexes), or oxonium salts (e.g., R30, A"). 

Photoinitiated cationic polymerization may also proceed by the AM mechanism if an HO-containing compound is present in the system. AM polymerization of cyclohexene oxide was used to prepare polymer/clay nanocomposite by photopoiymerization of cydohexene oxide in the presence of montmoryllonite modified with ammonium salts containing -CH2CH2OH groups and (Ph)2T PFs" as photoinitiator. Upon irradiation protic add was formed that catalyzed AM propagation on HO groups. As a result, polymer chains were attached to clay surfaces and exfoliated stmctures were obtained. ... 

Another system espedally suited for the synthesis of high-molecular-wdght poly(BCMO) is the R3AI/H2O initiating system. " Kinetic studies revealed that for this system the rate of polymerization increases by increasing the ratio (H2O]/ [R3AI] up to 1/1. Hus indicates dearly that polymerization is initiated by protic add generated by interaction of water with Lewis add. 

Strong protic adds art through an easy protonation of the lactam amide group, while several metal halides, such as chro-mirrm, iron, alrrminum, tungsten, and calcium chlorides, can form complexes with lactams. It has been assumed that the O-coordination with Lewis adds activates lactam... 

Strong protic adds, such as H2SO4, sulfonic adds... 

Lewis adds, such as FeCls and SnCU, initiate polymerization in cooperation with protic adds, resulting from the reaction of those spedes with traces of water or other acid contaminations present in the S3 tem. Indeed, some Lewis acid-protic acid combinations are very effective as initiators. The question whether Lewis adds alone are capable of initiating ROP of siloxanes is still open. Studies of the polymerization of D3 in the presence of sterically hindered substituted pyridine used as a proton trap proved that some nonprotic spedes, such as RC(0)Cl-SbCls complex, ethylboron sesquitrifiate (Et3B2(OTf)3), and certain metal trifiates, can initiate polymerization of this monomer. Trimethylsilyl triflate was considered to be inactive without addition of free trifluoro-methanesulfonic (trifiic) add CF3SO3H (TfOH). However, Jallouli and Saam reported that, after a long induction period, TMSOTf initiated the polymerization of some... 

The activity of the initiator (protic add) maintains throughout the entire process (permanent initiation). 

Cationic potymerization of tydic silaethers is initiated by strong protic adds, such as Cp3S03H. The polymerization... 

Additionally, metal oxidation can be performed with protic adds in non-aqueous solvents. For instance, the interaction between metallic titanium and HBF4 in acetonitrile leads to the formation of the titanium(lll) complex,25 6 [Ti(MeCN)6l[BF4]3, Eq. 4.5 ... 

Certain low-valent metal carbonyls are oxidized easily with protic adds in non-aqueous media. Thus, [MofCO) ] in diglyme is oxidized by 100% formic acid with the formation of [Mo2(02CH)4). In a related reaction, [Mo(S03CF3)3] is prepared by boiling a [Mo(CO>6) suspension in an excess of HSO3CF3.28 It is reasonable to assume that if a similar reaction was performed in the presence of a strong donor solvent, ttie reaction would lead to the formation of a homoleptic solvento-complex. 

The tetrafluoroborate complex, [Cr(BF4)(NO)2(T -Cp)], is converted into the more stable salt, [Cr(NO)2(MeCN)(Ti5-Cp)][BF4L on treatment with MeCN. 5 Similarly, the interaction of the isoelectroniccomplex, [Fe(CO)2(Ti5-Cp)l2, with p-toluenesulphonic add in acetonitrile leads to oxidative deavage of the Fe-Fe bond and formation of the acetonitrile solvento-complex, [Fe(CO)2(MeCN)(Ti5-Cp)][C)3SC6H4Me].8 For this reaction it was reported that the protic add was responsible for oxidation of the complex. However, the evolution of molecular hydrogen was not observed. 

Together with triphenylcarbenium and silver salts, protic adds are used in hydride abstraction reactions. It has been shown that... 

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