Why Do Some CDRs Smell Like Almonds?

bertok asks: "I have several spindles of CD-Rs of various brands that I use at home and work, and some of them have a very strong almond odour when opened. Does anyone know what causes that? I know that Hydrogen Cyanide has a distinctive almond odour, but so does a range of other organic chemicals. Can any Slashdot readers with a chemistry background enlighten us as to the possible source of the smell?"

Comments

benzaldehyde

[mpweasel]

IANAChemist, but the son of one, and my best guess is that it's benzaldehyde left over from the production of the plastic.

http://www.bartleby.com/65/be/benzalde.html
htt p://www.bartleby.com/65/al/aldehyde.html

Re:Cyanide is used

[portege00]

It's not CYANIDE, it's CYANINE. Here's some more information on that:

http://www.cdrplanet.com/dye-layer.html

I'm pretty sure its oderless, too.

Re:Cyanide is used

[GigsVT]

Cyananine dye is named as such because it is cyan (bluish) in color, not because it is related to cyanide.

There is no cyanide.

[TitaniumFox]

...and quit spreading misinformation.

Firstly, a cyano group is simply a carbon atom bonded to a nitrogen atom with a triple bond. In the term cyanide, the ide simply identifies the CN as an ion. Hydrogen cyanide (HCN) is the colorless, poisonous gas that may, or may not smell like almonds. (Go ahead...smell it.)

The blue dye you are thinking about is called cyanine, which is simply the common name for 1,1-diisoamyl-4,4-cyanine iodide.

If you go here, you will see a structure of cyanine. The only nitrogen present in the chemical is firmly rooted in a benzine ring (called pyridine). It's not going anywhere, and there's certainly no cyanide.

Additionally, the other dye used in CDRs is called phthalocyanine. Structure here. As you can see, the molecule is circular and the CN groups are in rings and in bonds between the ring structures. No hydrogen cyanide will be evolved.

While this doesn't answer why CDRs smell like almonds after/while they are being burned (do they? I've never smelled that), it does cast away some of the misperceptions.

Cyanide does not smell like almonds

[Muhammar]

You can smell HCN when you sniff at the bottle with cyanide or cyanoborohydride - it is a bitter, nasty, almnost pyridine-like stink. Sure, cyanide is in bitter almonds and peach inner seeds, it makes part of their flavour.

What you smell is the common almond-food flavor (Dr.Pepper flavor)- benzaldehyde, most likely. They add this stuff into some furniture polish, too.
The other possible, very similar almond-smelling substances are nitrobenzene (poisonous) and benzonitrile.

I think it is some kind of solvent/paint additive which they use for printing the label on the CD, definitely not anything essential for the CD manufacture.

[And, cyanin is a non volatile dye and has nothing to do with cyanide - the name is similar because of the greek word cyanos=blue]

Re:Cyanide does not smell like almonds

[grondu]

Sure, cyanide is in bitter almonds and peach inner seeds, it makes part of their flavour

It's not free cyanide, it's in the compound amygdalin.

From the Poison Information Centre of Singapore: Commonly occurs in the kernels of almonds, apricots, cherries, peaches, apples, as well as the stems, leaves and roots of many rose (Rosaceae) family species.. A cyanogenic glycoside compound. It is known that the hydrolysis of amygdalin can give rise to hydrogen cyanide.

Normally, the presence of amygdalin alone in these kernels is not dangerous It is only in the crushed, moistened seed which releases an enzyme can the hydrolysis of amygdalin be effected.

Acute intoxication and death had been reported in children following ingestion of apricot seeds which are capable of releasing 217mg of cyanide per 100 g of moist seeds.

The smell is definitely real

[0x0d0a]

No, I've actually wondered the same thing myself for a while (though it's possible that Taco thought it was bogus and would be a great post to use as April 1 material).

When I open a new, shrinkwrapped (and therefore sealed) spindle of CDs, most brands have a strong smell that is very similar to that of almonds. It goes away if you leave the thing open for a while, but if you seal a spindle for a while, you can smell it a bit when you open it later. (Presumably, the scent is coming from some sort of decomposition going on in the CD, then, rather than just gas from the manufacturing process). I usually a use a variety of generic not-very-intense blue CDRs. I don't remember smelling almonds with the old gold CDRs I used to use, though it's possible that I just didn't notice. I've certainly never noticed it with silver pressed audio CDs. My CDRs are kept in clear spindles (in sunlight) -- I vaguely remember that sunlight tended to have some sort of impact on CDRs, so it may be that it simply doesn't affect people who keep them in those black binders.

I also remembered the "cyanide smells like almonds" tidbit, and wondered if that might have something to do with it, but some chem people here have said that phalocyanine (or whatever the stuff is) is quite different and doesn't have an odor.

But, yes, I can vouch that this is definitely fact, not an April 1 joke.