ChemAxon b124dd5f17

28-10-2004 08:35:45

Recieved via email
I had a question about the calculator tools of MarvinView and MarvinSketch. I was wondering what the units on the numbers that these calculations are? Specifically the units for the Polar Surface Area (TPSA), pKa, and log(P) (if there are units).

User 851ac690a0

28-10-2004 16:53:41


TPSA [Angström^2]

logP and pKa are without units.

User 34a147f5dc

29-10-2004 18:44:31

Jozsi, is there a listing somewhere of each calculation and the units the answer is given in (for all the calculations)?

User 851ac690a0

02-11-2004 15:38:14


charge is expressed in atomic unit [e] (proton charge)

refractivity 10^6*[m^3/mol]

energy parameters obtained from simple Hückel calc. is expressed as 'beta'.

polarizability [Angström^3]

logD is without unit

Short description from the calculations are given here. http://www.chemaxon.com/marvin/chemaxon/marvin/help/calculator-plugins.html

(units are not mentioned, we will correct this shortcoming)

User d476481081

11-03-2014 10:24:18

Hi there, 

I followed your previous link, but the page no longer exists... I am looking for the units of the orbital electronegativity calculators (which we deploy in Knime). The units are outside of the traditional Pauling values, so I assume you are using a different unit system?

Thanks in advance for your help 

User 851ac690a0

16-04-2014 09:53:42



Sorry for  the delayed answer.

The unit of  the orbital electronegativiy is [eV] in our calculation.

Gasteiger's electronegativity value based on  the Mulliken's electronegativity value.


To convert the orbital electronegativity value into the most popular Pauling's electronegativity scale is possible with the next expression which is a regresison relation between Pauling's and Mulliken's electronegativity.


 Xp  = 0.337*Xg-0.2072  (Eq.1) 


Where Xg is the orbital electronegativity calulated by us. 

            Xp is the electronegativy value on the Pauling scale.


For example:  

The molecule is given on the attached figure with the calculated Xg values.

The calculated orbital electornegativity value of the "Cl" atom is 

Xg,Cl= 10.89

According to the (Eq. 1) the orbital electronegativity of the "Cl" atom on the Pauling scale is:

Xp,Cl = 0.337*10.89 - 0.2072 = 3.46


Thanks for reporting this shortcoming.

We will supplement the user's documentation  according to this..