Relative properties of Hexane vs Septane? 3

[nomorepatience]

Does anyone know of any difference in the properties of Hexane to that of Septane?

Realtive solubility in water?
Attraction to C02?
Does one easily attach to a Benzene ring and the other not?
Boiling point?
Vapour point?

Thanks in advance.

 

[mbeychok]

Nomorepatience:

1 -- I assume, that by "septane", you mean the alkane hydrocarbon with 7 carbon atoms. The correct name is "heptane"

2 -- There is no such thing as "the vapor point". There is "the vapor pressure" of a liquid at a specific temperature.

Here are the boiling points of hexane and heptane at atmospheric pressure (14.696 psia):

Hexane boiling point = 156 °F at atmospheric pressure
Heptane boiling point = 209 °F at atmospheric pressure

Here are the vapor pressures of hexane and heptane at 70 °F and also at 140 °F:

Hexane vapor pressure = 2.4 psia at 70 °F
Heptane vapor pressure = 0.7 psia at 70 °F

Hexane vapor pressure = 11 psia @ 140 °F
Heptane vapor pressure = 4 psia @ 140 °F

As you can see Hexane is significantly more volatile than heptane (i.e, it has a lower atmospheric boiling point and it has higher vapor pressures at two example temperatures).

As for your other questions:

Solubility in water: Both would very, very low water solubilities

Attraction to CO2: I have no idea, nor do I understand what you mean by "attraction" to CO2. Do you mean the solubility of CO2 gas in liquid hexane and liquid heptane?

Attachment to benzene: I have no idea, nor do I understand what you mean by "easily attach to benzene". I don't know how one would measure the "ease of attachment".

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[kenvlach]

Aqueous solubilities & Henry's Law constants are given in CRC Handbook of Chemistry and Physics.
Solubilities at 25 ^oC:
Hexane 0.0011 wt% (0.00136 at 60 ^oC)
Heptane 0.00024 wt% (0.0003 at 0^oC, 0.00025 at 40^oC)

Relative attraction to carbon dioxide (some hydrogen bonding to the O atoms) would follow the trend with water, while relative attraction toward benzene (aromatic, non-polar) would probably be inverse cf. water. But, better to look up the phase diagrams of these systems.

 

[owg]

According to a set of curves based on work by Mcketta, N-Hexane solubility in water is about 96 ppmw and N-Heptane is about 102 ppmw at 60 deg F.

HAZOP at

http://www.curryhydrocarbons.ca

 

[nomorepatience]

Yes, heptane. Sorry. That's what you get for trying to do five things at once.

I'm drilling an oilwell and getting CO2 and benzene associated with formation water and heptane seemingly associated with CO2 peaks but no hexane at all.

It's not an equipment fault. I was looking for reasons I might get heptane but not hexane. I'm not a chemist either so I'm off my subject (geology) here.

Thanks for the information anyway, much appreciated.