I have a process that requires pH~14-14.5 to work. I’ve been achieving this with concentrated NaOH solutions, but the Na cations are later causing side reactions which are detrimental. Is there any organic base/non-alkali base that has the solubility in water and pKa to reach these pH values?
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1$\begingroup$ Do you mean non-alkali metal, i.e. non Group I metal? All "bases" are alkalis. $\endgroup$– DrMoishe PippikCommented Mar 15, 2018 at 23:01
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2$\begingroup$ There's a whole lot of them, so better edit your question quickly, 'cause right now you could get either simple yes as an answer or you might find a whole book somewhere. $\endgroup$– MithoronCommented Mar 16, 2018 at 0:16
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$\begingroup$ Did you try KOH? LiOH? $\endgroup$– Oscar LanziCommented Mar 16, 2018 at 1:26
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$\begingroup$ K and Li are Alkali metals... $\endgroup$– TungstenBronzeCommented Mar 16, 2018 at 2:38
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1$\begingroup$ @tungstenbronze What I meant was, you said sodium is a problem, so why blame all alkali metals? Are they all problems? $\endgroup$– Oscar LanziCommented Mar 16, 2018 at 8:12
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2 Answers
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Tetramethylammonium hydroxide
This is a strong base like NaOH.
See Behavior of Polyethylene Oxide Based Nonionic Surfactants in Silicon Processing Using Alkaline Solutions J. Electrochem. Soc. 1995 volume 142, 621-627:
alkaline cleaning solutions based on quarternary ammonium hydroxides such as choline ($pK_b = 0.1$) and tetramethyl ammonium hydroxide ($pK_b = 0$)
and Ceramic Nanomaterials and Nanotechnology II which says:
In this research, tetramethylammonium hydroxide (TMAH) was used, instead of KOH, to adjust pH of the precursor solution to 14.0
Also, TETRAMETHYLAMMONIUM HYDROXIDE Journal of the Chemical Society (1905):
An estimation of the strength of the base by means of the velocity of saponification of methyl acetate in N/80 solution showed that it was somewhat weaker than sodium hydroxide. The velocity constants obtained at 25 [degrees] were 0.0106 and 0.0115 respectively, so that if the strength of sodium hydroxide is represented as 100, that of tetramethylammonium hydroxide, under the above conditions, will be represented by 92.
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1$\begingroup$ @OscarLanzi this thesis says pKb is zero digital.library.unt.edu/ark:/67531/metadc822794/m2/1/high_res_d/… $\endgroup$– DavePhDCommented Mar 16, 2018 at 23:47
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1$\begingroup$ @OscarLanzi I think Wikipedia is wrong. Another reference says "In this research, tetramethylammonium hydroxide (TMAH) was used, instead of KOH, to adjust pH of the precursor solution to 14.0". books.google.com/… $\endgroup$– DavePhDCommented Mar 17, 2018 at 1:43
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$\begingroup$ @OscarLanzi I added better references to the answer. $\endgroup$– DavePhDCommented Mar 17, 2018 at 18:33
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Water solutions of amines can get to pH+ 12 or so. Piperidine, $\ce{(CH2)5NH}$, is about pH 11.
To get much higher pH+ requires somewhat exotic fluorinated organic chemicals, such as $\ce{9-COO-Me-fluorene}$, $\ce{(4-Me-C6F4)2CHCN}$ or $\ce{(4-Me-C6F4)(C6F5)CHCN}$. See Paenurk et al, A unified view to Brønsted acidity scales: do we need solvated protons? and download the PDF for an interesting explanation.
answered Mar 15, 2018 at 23:48
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$\begingroup$ You shouldn't make a "sentence link" especially with what looks like acids; you mean their salts or what? $\endgroup$– MithoronCommented Mar 16, 2018 at 0:20