3,3 ,5,5 -Tetramethyl-4,4 -biphenol

Also, multi-block PAES copolymers with pendant quaternary ammonium groups have been synthesized [114]. One block is made from 3,3, 5,5 -tetramethyl-4,4 -biphenol and 4,4 -difluorodiphenyl sulfone. The other block is made from bis(4-hydroxyphenol) sulfone and 4,4 -difluorodiphenyl sulfone. After combining the two blocks, the pendant methyl groups in the 3,3, 5,5 -tetramethyl-4,4 -biphenol moiety are bro-momethylated with A-bromosuccinimide and finally quaternized. The materials are used for alkaline fuel cells. 

The crosslinking agent is prepared from 3,3, 5,5 -tetramethyl-4,4 -biphenol and epichlorohydrin, as shown in Figure 16.4. 

Novel 2,2, 6,6 -tetrabromo-3,3, 5,5 -tetramethyl-4,4 -biphenol (TBTMBP) and its epoxy derivatives [28] were synthesized to incorporate the stable meta-terminated phenol moiety into epoxy resin systems. In electronic encapsulation and laminate applications, epoxy systems derived from TBTMBP exhibit superior hydrolytic and thermal stability as compared with the conventional ortho-bromi-nated epoxy resins. These properties have resulted in an extended device life for semiconductors and a high Tg with excellent blister resistance for the printed circuit board, while meeting flame retardancy requirements as well. 

Some simple biphenols equipped with methyl groups, e.g., 3,3, 5,5 -tetramethyl-2,2 -biphenol 38, have attracted attention as important components of highly potent ligand systems [75-86]. Remarkably, the sustainable synthesis of such biphenols is rather challenging despite their simple scaffolds. In particular, methyl-substituted phenols are prone to side reactions. This is especially the case when 2,4-dimethyl-phenol (37) is oxidatively treated. Upon anodic conversion 37 is preferably transformed into polycyclic architectures [87]. Direct electrolysis in basic media provided only traces of the desired biphenol 38 and the dominating components of the product mixture consisted of Pu in meter s ketone 39 and the consecutive pentacyclic spiro derivative 40 [88]. For an efficient electrochemical access to 3,3, 5,5 -tetramethyl-2,2,-biphenol (38) we developed a boron-based template strategy [89, 90]. This methods requires a multi-step protocol but can be conducted on a multi-kilogram scale (Scheme 17). 

The oxidative ortho-coupling reaction of 2,4-dimethylphenol (12) became of interest for our laboratories since a demand for this particular compound was recognized (Bartsch et al. 2005). Initial studies including the direct electrolysis in basic media led only in traces to the desired 3,3, 5,5/-tetramethyl-2,2/-biphenol... 

Tetrabromo-3,3 /5,5 -Tetramethyl-p,p Biphenol (TTB) n. An aromatic bromi-nated flame retardant synthesized easily by a two-step process from 2,6-dimethylphe-nol. The unusual chemical structure of TTB enables its use as both a reactant and additive flame retardant. It has been used... 

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