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Fery
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Hi AvBayer, both have their melting points distinct enough (ethoxy 37-38 C, methoxy 74-75 C) and if e.g. the ethoxy was contaminated with methoxy then
its already quite low m.p. would be depresses so much that it could perhaps even not crystallize. I successfully synthesized ethoxy but using C2H5I
(from 36,0 g 2-naphthol my yield was 27,8 g of 2-ethoxy-naphthalene, loses perhaps due to tedious steam distillation so I left some unknow part of it
in the distillation flask). I like the ethoxy more as it has more orange scent. I purified both methoxy as well ethoxy by steam distillation (ethoxy
passes condenser easier due to lower m.p. than methoxy, anyway I suggest to use a condenser with the most wide inner tube diameter you have). I
crystallized small amount of methoxy from methanol (there are difficulties described in the above link which I posted - too concentrated solution not
good crystals that was IIRC 4,0 g of methoxy in 10 ml of methanol, diluted twice so 4,0 g of methoxy in 20 ml of methanol - then yield of crystals
only 50% so a half the methoxy stayed in the methanol mother liquor - most of it could be of course recovered from the mother liquor). I wonder
whether ethoxy could be crystallized in a way like dissolving in methanol at 30 C and cooling to -10 or -20 but I have never tried that (I
crystallized only methoxy). It would be great to know which solvent to use for ethoxy in which it would be soluble enough at 30 C and very low
solubility at 0 or few deg. below zero.
I also tried allyloxy and it has even lower m.p. so I got liquid product at room temperature and its approximate m.p. was around fridge temperature 4
C but I do not know how pure my allyloxy product was.
Damn the longer carbon chain the lower m.p., some kind of unexpected anomaly.
[Edited on 11-12-2023 by Fery]
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Diachrynic
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Quote: Originally posted by AvBaeyer  | | I have executed the same reaction under several conditions including that reported by Diachrynic and have never achieved a yield in excess of 35% of
crystalline 2-ethoxynaphthalene melting at 34-36 C. My reactions were all run using 5.0 g of 2-naphthol (mp 120-121 C), undenatured absolute ethanol
and 96% sulfuric acid (by titration). I use hexane to extract the product from the work up mixture. The crystalline product is isolated directly from
the hexane extract after a brine wash, drying, and evaporation of the hexane. I can recover about 85% of the unreacted 2-naphthol which is extremely
difficult to filter. |
Hello AvBaeyer, I'm sorry to hear you haven't had good success with my method. The
ethanol I used was undenatured and dried over molsieves 3A, so it should have been quite dry. This ethanol I have used many times for other
experiments, so there is no doubt in my mind that it is, in fact, ethanol.
I don't know why it gave such a low yield for you. I will report the melting point as soon as possible, which will be in about one week. I can also
check the boiling point of my ethanol. But I wouldn't expect any surprises, if I am honest.
we apologize for the inconvenience
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Texium
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Not really. That’s a pretty
typical trend for molecules like this. Longer “greasier” alkyl chains attached to aromatic compounds tend to disrupt the crystal structure and
lower the melting point. It’s sort of an inverse parabola though. Eventually melting point will start to go up again, as sheer molecular weight
increases, but the solids will tend to be waxier and less crystalline than their methyl or ethyl counterparts.
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DraconicAcid
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| Quote: Originally posted by Texium | | Not really. That’s a pretty typical trend for molecules like this. Longer “greasier” alkyl chains attached to aromatic compounds tend to disrupt
the crystal structure and lower the melting point. |
Agreed. There's a number of methyl esters (cinnamate, anisate, etc) that have significantly higher melting points than the ethyl esters, for exactly
the same reason.
Methyl cinnamate is easy to purify by recrystallization. Ethyl cinnamate, I couldn't crystallize it even in a -20 oC freezer.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Diachrynic
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It turned out more than a week, but the melting point was 36 °C. Which is about 1.5 °C below literature, I guess there is some cyclohexane still in
it, but close enough to confirm identity imo.
we apologize for the inconvenience
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