[appamo]

what's the difference between hemiacteal or hemiketals?? and based on the structure in the attachment, how to identify it as being acetal or ketal or hemi...??pls...really need help

[Doc Oc]

Hemiketals come from ketones, hemiacetals from aldehydes.

The simplest way to know whether something is a ketal or acetal is to see if the protected carbon has a H.  If it does, it's an acetal, if not, ketal.

[appamo]

Hemiketals come from ketones, hemiacetals from aldehydes.

The simplest way to know whether something is a ketal or acetal is to see if the protected carbon has a H.  If it does, it's an acetal, if not, ketal.

but do u know how to identify those structure i attached?

[fledarmus]

Wherever you see two carbons attached to the same oxygen, erase those two bonds and replace them with a double-bonded carbon. Is the result a ketone or aldehyde?

Doc Oc gave you the simplest method, now it's your turn - show us your guesses and explanations and we'll help. Nobody is just going to give you the answers - that's not what this forum is for.

[fledarmus]

Oh, for your other question - the difference between a hemiacetal or hemiketal and an acetal or ketal, is that the hemi means only one alkoxy group has added to the carbonyl - you will have a carbon with an -OR group and an -OH group attached to it.

[appamo]

Oh, for your other question - the difference between a hemiacetal or hemiketal and an acetal or ketal, is that the hemi means only one alkoxy group has added to the carbonyl - you will have a carbon with an -OR group and an -OH group attached to it.

i get what hemi means but wht abt ketal and acetal? in internet and book they said ketal is old time usage. and i thought that acetal is derived from alldehyde while ketone derive frm ketones? -confuse-

[fledarmus]

Yes, the way I learned it (and I certainly qualify as old-time!), aldehydes make acetals and ketones make ketals. The way IUPAC seems to like it now, a ketal is just an acetal in which the C-H bond is replaced with a C-C bond.



(Wikipedia image)

[Borek]

i wht abt frm

Please use proper English, text speak is against forum rules.

[appamo]

Yes, the way I learned it (and I certainly qualify as old-time!), aldehydes make acetals and ketones make ketals. The way IUPAC seems to like it now, a ketal is just an acetal in which the C-H bond is replaced with a C-C bond.



(Wikipedia image)

oh i see...thank you very much

[appamo]

Yes, the way I learned it (and I certainly qualify as old-time!), aldehydes make acetals and ketones make ketals. The way IUPAC seems to like it now, a ketal is just an acetal in which the C-H bond is replaced with a C-C bond.



(Wikipedia image)

why ketal consider as old time usage? sorry to ask again

[orgopete]

Re: nomenclature, "old time" vs IUPAC

Frankly, I prefer systematic nomenclature. If you know systematic nomenclature (it isn't a kind of nomenclature), then you can convert from a name to a structure. I would avoid using an IUPAC name for cholesterol or for a derivative of cholesterol. But, it is very helpful to know how to modify the name of cholesterol or a derivative to name a new compound. A reason I prefer a simple understanding of how things are named is that even though the IUPAC organization can write rules for nomenclature, and have even modified them, this does not result in any historical revisions. That paper in the Journal of the American Chemical Society written in 19XX may contain the nomenclature of the time or simply preferred by the author. Any change in the IUPAC rules does not result in a change in the journal. It is helpful to understand the names. Enough of that.

If you started with acetone and made the dimethyl ketal, that would be common nomenclature. In IUPAC, you would start with propanone and make 2,2-dimethoxypropane. Dimethoxypropane would be a ketal, though it would not be part of its name.

[appamo]

Re: nomenclature, "old time" vs IUPAC

Frankly, I prefer systematic nomenclature. If you know systematic nomenclature (it isn't a kind of nomenclature), then you can convert from a name to a structure. I would avoid using an IUPAC name for cholesterol or for a derivative of cholesterol. But, it is very helpful to know how to modify the name of cholesterol or a derivative to name a new compound. A reason I prefer a simple understanding of how things are named is that even though the IUPAC organization can write rules for nomenclature, and have even modified them, this does not result in any historical revisions. That paper in the Journal of the American Chemical Society written in 19XX may contain the nomenclature of the time or simply preferred by the author. Any change in the IUPAC rules does not result in a change in the journal. It is helpful to understand the names. Enough of that.

If you started with acetone and made the dimethyl ketal, that would be common nomenclature. In IUPAC, you would start with propanone and make 2,2-dimethoxypropane. Dimethoxypropane would be a ketal, though it would not be part of its name.

oh i see....thank you