Yellow/green color of acetone and MEK

[Wilco Oelen]

Hello,

I have some acetone, stored in a transparent colorless glass bottle in
a dark cabinet. The acetone has turned light yellow/green within
approximately one year of storage. When I purchased the acetone it was
completely colorless.
Before I did the acetone in the bottle, it was cleaned very well with
hot water, then rinsed with distilled water, allowed to (almost)
completely dry and finally rinsed two times with a small amount of
acetone.

A similar, even stronger, observation I have made with MEK (methyl
ethyl ketone). I separated 100 ml of this and poured this in a small
glass bottle. This MEK also has turned yellow/green in just a few
months of storage. The remaining MEK in the original bottle still is
colorless. The MEK also is stored in a dark cabinet. The bottles, in
which the MEK is stored are cleaned in a similar way as the acetone
bottle, but now with two finals rinses with MEK.

Any idea what the source of the color is? Are ketones not stable on
storage?

Wilco Oelen

[Steve Turner]

Post by Wilco Oelen
Hello,
I have some acetone, stored in a transparent colorless glass bottle in
a dark cabinet. The acetone has turned light yellow/green within
approximately one year of storage. When I purchased the acetone it was
completely colorless.
Before I did the acetone in the bottle, it was cleaned very well with
hot water, then rinsed with distilled water, allowed to (almost)
completely dry and finally rinsed two times with a small amount of
acetone.
A similar, even stronger, observation I have made with MEK (methyl
ethyl ketone). I separated 100 ml of this and poured this in a small
glass bottle. This MEK also has turned yellow/green in just a few
months of storage. The remaining MEK in the original bottle still is
colorless. The MEK also is stored in a dark cabinet. The bottles, in
which the MEK is stored are cleaned in a similar way as the acetone
bottle, but now with two finals rinses with MEK.
Any idea what the source of the color is? Are ketones not stable on
storage?

They should be stable. I suspect you either a) had impurities in the
acetone, which over time degraded or caused degradation of the
acetone, or b) used a bottle cap with a liner that introduced some
colored contaminants.

Steve Turner

[Muhammar]

Ketones should be stable if pure. Acids (and bases) catalyse
dimerisation. The first step (aldol reaction) is reversible and
strongly shifted towards starting material, the second step (water
elimination) is irreversible and is catalysed by acids also. The
formed 3-methyl-2-butene (mesytylen oxide) is yellow.

This is my best guess.

Post by Wilco Oelen
Hello,
I have some acetone, stored in a transparent colorless glass bottle in
a dark cabinet. The acetone has turned light yellow/green within
approximately one year of storage. When I purchased the acetone it was
completely colorless.
Before I did the acetone in the bottle, it was cleaned very well with
hot water, then rinsed with distilled water, allowed to (almost)
completely dry and finally rinsed two times with a small amount of
acetone.
A similar, even stronger, observation I have made with MEK (methyl
ethyl ketone). I separated 100 ml of this and poured this in a small
glass bottle. This MEK also has turned yellow/green in just a few
months of storage. The remaining MEK in the original bottle still is
colorless. The MEK also is stored in a dark cabinet. The bottles, in
which the MEK is stored are cleaned in a similar way as the acetone
bottle, but now with two finals rinses with MEK.
Any idea what the source of the color is? Are ketones not stable on
storage?
Wilco Oelen

[Bob]

Post by Wilco Oelen
Hello,
I have some acetone, stored in a transparent colorless glass bottle in
a dark cabinet. The acetone has turned light yellow/green within
approximately one year of storage. When I purchased the acetone it was
completely colorless.
Before I did the acetone in the bottle, it was cleaned very well with
hot water, then rinsed with distilled water, allowed to (almost)
completely dry and finally rinsed two times with a small amount of
acetone.
Any idea what the source of the color is?

How about the bottle lid?

bob

[Wilco Oelen]

Thanks, you all, for the replies. I did not even think of the bottle
caps. I also cleaned these, but of course, these may slowly react with
acetone or MEK. Probably this is the answer to my question and this may
also explain why the MEK in the original bottle still is colorless.

What kind of caps is suitable for this kind of liquids? Apparently the
caps must be selected with great care.

Wilco

[Steve Turner]

Post by Wilco Oelen
Thanks, you all, for the replies. I did not even think of the bottle
caps. I also cleaned these, but of course, these may slowly react with
acetone or MEK. Probably this is the answer to my question and this may
also explain why the MEK in the original bottle still is colorless.
What kind of caps is suitable for this kind of liquids? Apparently the
caps must be selected with great care.

In my experience, it is common for contaminants to "hide" underneath
the cap liner -- between the liner and the cap itself. Because you
can't see these materials, you can accidently use what is effectively
a "dirty" cap. For that reason, I never re-use bottle caps.

A type of cap used commonly in the U.S. is called "poly seal." This
is a standard Bakelite cap with a conical polyethylene insert. These
seal better than flat liners, especially after many re-closings of the
bottle, which can tend to compress a flat liner and remove its
elasticity. These types of caps are inert to common organic solvents,
and you should have no trouble with one if it's clean to begin with.

Steve Turner