[nirvan]

hi friends
do u know melting point of these compounds I have searched chemspider, MSDS and also I have searched internet by their name and formula but I didn't find any thing , I would be grateful if u introduce me the paper, book or anywhere that you have find the mp. tank u for your help
the structures are painted in chem draw and the mp.s are reported by chemdraw which seems 

[Dan]

I had a quick look and can't find anything either, the compounds appear to be novel. Are you sure you have drawn them correctly, and are you sure they've been made before?

Did ChemDraw predict m.p. and b.p.? This seems like a useless feature!

[discodermolide]

I had a quick look and can't find anything either, the compounds appear to be novel. Are you sure you have drawn them correctly, and are you sure they've been made before?

Did ChemDraw predict m.p. and b.p.? This seems like a useless feature!

ChemDraw gives for benzoic acid, as an example, a MPt of 355.17°K, and a BPt. of 522.68°K; Wikipedia reports 396°K and 523°K respectively.
Make of that what you will!!!!!

[Enthalpy]

I confirm (every?) software gives often sensible boiling points but fails completely on melting points.

My hypothesis: solidification depends on all possible orientations, positions, and if possible conformations, of groups of many molecules. This means a new piece of software, that may well require heavy computing, could possibly predict melting points, but additive rules are bound to fail.

[discodermolide]

I confirm (every?) software gives often sensible boiling points but fails completely on melting points.

My hypothesis: solidification depends on all possible orientations, positions, and if possible conformations, of groups of many molecules. This means a new piece of software, that may well require heavy computing, could possibly predict melting points, but additive rules are bound to fail.

They certainly do not take crystal modifications into account in their calculations!

[nirvan]

thanks for the replies

Are you sure you have drawn them correctly, and are you sure they've been made before?
Did ChemDraw predict m.p. and b.p.? This seems like a useless feature!

yes I did that correctly, but I guess these compounds are made before,
the m.p. and b.p. s are predicted by chemdraw  as you said some of them seems wonderful

but I can't exactly understand why friends say that predicting b.p. is easier than m.p. for a software, I would be grateful if anyone explain it for me

[discodermolide]

thanks for the replies

Are you sure you have drawn them correctly, and are you sure they've been made before?
Did ChemDraw predict m.p. and b.p.? This seems like a useless feature!

yes I did that correctly, but I guess these compounds are made before,
the m.p. and b.p. s are predicted by chemdraw  as you said some of them seems wonderful

but I can't exactly understand why friends say that predicting b.p. is easier than m.p. for a software, I would be grateful if anyone explain it for me

As I said above a compound can crystallize in many different crystal modifications, each has a different MPt. Thus it is impossible to calculate the MPt with any degree of certainty.
Look up crystal modifications on google or the like.

[fledarmus]

thanks for the replies

Are you sure you have drawn them correctly, and are you sure they've been made before?
Did ChemDraw predict m.p. and b.p.? This seems like a useless feature!

yes I did that correctly, but I guess these compounds are made before,
the m.p. and b.p. s are predicted by chemdraw  as you said some of them seems wonderful

but I can't exactly understand why friends say that predicting b.p. is easier than m.p. for a software, I would be grateful if anyone explain it for me

The contributions for entropy in liquids and gases are fairly easy to predict, since both liquids and gases are disordered structures. Where the boiling point calculations do fail to adequately predict boiling points tends to be where the liquids have strong enough intermolecular forces that entropy becomes a factor.

Solids are highly ordered and entropy is not only significant but very dependent on the exact structure of the solid. To get accurate mp predictions would require either a training set of near analogs for which melting point data has been measured, or a significant amount of computational chemistry docking calculations to predict the lowest energy conformation of the molecules and the interactions between molecules over a wide range of possible orientations.

[the.khemist.ds]

Hi,

I've performed a search on ChemSpider for the basic framework that you showed in your document. The link is below (Please note it will likely expire in a couple of days)
http://www.chemspider.com/Search.aspx?rid=22044438-4bc4-4f99-82ab-358bd6649e6e

You can access some predicted data (but not m.p.) on structures that are not in ChemSpider using the prediction services:

http://www.chemspider.com/Services.aspx

The structures that you've drawn look like they are probably known (ie have been synthesised before) but not so commonly used that you would be likely to find experimental data for them anywhere other than the primary literature.

Dave