In the view of electronegativity, P-O-H loses its proton easily whereas in the point of bond length, P-H will lose its proton quickly. So that doubt arises now. Among these two factors, which one decide the fate?
I think that electronegativity must be considered first.
Well, as the radius of the atom increases electronegativity decreases and as the atom's radius increases the bond length increases, what is concluded is the following: as the bond length increases electronegativity decreases.
So for the proton, when the bond length increases, the H+ will be releases easily but the electronegativity decreases so the H+ will not be released easily. So they don't work together in the case of the proton.
Because as we know, if the electron of the H is more attracted to the atom which the H is bonded to, then the H+ will be released easily (compare HF and HCl) which makes sense... so electronegativity is stronger than the factor of bond length.
I think the electronegativity in this case has a larger component of responsibility in the loss of the proton ... a point for this is the amount of available oxygen that electrons can coordinate the hydrogen and / or metal ... an analysis of the atoms electronegativities present in these groups can clarify this issue.
Compare the pKa of phosphine (not an acid in aqueous solution) and phosphoric acid to answer your question.
Check for the stability of conjugate base formed after loosing the proton, since PO- is more stable than P-, thus POH should leave its proton first.
It is not a simply matter of electronegativity, but of how the charge remaining on the anion upon deprotonation can be stabilised.
which one loses its proton easily?
Loses or transfers?. If transfers, where and under what conditions?
In POH the H is a proton whereas in P-H it is a hydride. There is a significant difference. Are you simply referring to the loss of H or are you specific about it being lost as H+ ?
Mr. Antony,
According to theoretical analysis carried out (attachment) for systems PH3 and PH2OH, the energy needs for dissociation of the (P)O-H bond is lower than, this one for the dissociation of the (H2)P-H bond.
Bellow you can find additional computational data.
H
-------------------
- Thermochemistry -
-------------------
Temperature 298.150 Kelvin. Pressure 1.00000 Atm.
Atom 1 has atomic number 1 and mass 1.00783
Molecular mass: 1.00783 amu.
Zero-point vibrational energy 0.0 (Joules/Mol)
0.00000 (Kcal/Mol)
VIBRATIONAL TEMPERATURES: (KELVIN)
Zero-point correction= 0.000000 (Hartree/Particle)
Thermal correction to Energy= 0.001416
Thermal correction to Enthalpy= 0.002360
Thermal correction to Gibbs Free Energy= -0.010654
Sum of electronic and zero-point Energies= -0.500273
Sum of electronic and thermal Energies= -0.498856
Sum of electronic and thermal Enthalpies= -0.497912
Sum of electronic and thermal Free Energies= -0.510927
E (Thermal) CV S
KCAL/MOL CAL/MOL-KELVIN CAL/MOL-KELVIN
TOTAL 0.889 2.981 27.392
ELECTRONIC 0.000 0.000 1.377
TRANSLATIONAL 0.889 2.981 26.014
ROTATIONAL 0.000 0.000 0.000
VIBRATIONAL 0.000 0.000 0.000
Q LOG10(Q) LN(Q)
TOTAL BOT 0.795368D+05 4.900568 11.283975
TOTAL V=0 0.795368D+05 4.900568 11.283975
VIB (BOT) 0.100000D+01 0.000000 0.000000
VIB (V=0) 0.100000D+01 0.000000 0.000000
ELECTRONIC 0.200000D+01 0.301030 0.693147
TRANSLATIONAL 0.397684D+05 4.599538 10.590828
ROTATIONAL 0.100000D+01 0.000000 0.000000
-------------------------------------------------------------------
PH3
-------------------
- Thermochemistry -
-------------------
Temperature 298.150 Kelvin. Pressure 1.00000 Atm.
Atom 1 has atomic number 15 and mass 30.97376
Atom 2 has atomic number 1 and mass 1.00783
Atom 3 has atomic number 1 and mass 1.00783
Atom 4 has atomic number 1 and mass 1.00783
Molecular mass: 33.99724 amu.
Principal axes and moments of inertia in atomic units:
1 2 3
EIGENVALUES -- 13.84020 13.84032 15.74502
X 1.00000 0.00000 -0.00001
Y 0.00000 1.00000 -0.00001
Z 0.00001 0.00001 1.00000
THIS MOLECULE IS AN ASYMMETRIC TOP.
ROTATIONAL SYMMETRY NUMBER 1.
ROTATIONAL TEMPERATURES (KELVIN) 6.25811 6.25805 5.50100
ROTATIONAL CONSTANTS (GHZ) 130.39853 130.39736 114.62299
Zero-point vibrational energy 61806.8 (Joules/Mol)
14.77219 (Kcal/Mol)
VIBRATIONAL TEMPERATURES: 1507.15 1666.40 1666.46 3330.86 3346.55
(KELVIN) 3349.80
Zero-point correction= 0.023541 (Hartree/Particle)
Thermal correction to Energy= 0.026444
Thermal correction to Enthalpy= 0.027388
Thermal correction to Gibbs Free Energy= 0.002471
Sum of electronic and zero-point Energies= -343.123262
Sum of electronic and thermal Energies= -343.120359
Sum of electronic and thermal Enthalpies= -343.119415
Sum of electronic and thermal Free Energies= -343.144332
E (Thermal) CV S
KCAL/MOL CAL/MOL-KELVIN CAL/MOL-KELVIN
TOTAL 16.594 6.767 52.442
ELECTRONIC 0.000 0.000 0.000
TRANSLATIONAL 0.889 2.981 36.502
ROTATIONAL 0.889 2.981 15.763
VIBRATIONAL 14.817 0.806 0.176
Q LOG10(Q) LN(Q)
TOTAL BOT 0.729819D-01 -1.136785 -2.617544
TOTAL V=0 0.491179D+10 9.691240 22.314905
VIB (BOT) 0.150669D-10 -10.821976 -24.918520
VIB (V=0) 0.101403D+01 0.006049 0.013928
ELECTRONIC 0.100000D+01 0.000000 0.000000
TRANSLATIONAL 0.779159D+07 6.891626 15.868555
ROTATIONAL 0.621677D+03 2.793565 6.432421
-------------------------------------------------------------------
PH2OH
-------------------
- Thermochemistry -
-------------------
Temperature 298.150 Kelvin. Pressure 1.00000 Atm.
Atom 1 has atomic number 15 and mass 30.97376
Atom 2 has atomic number 8 and mass 15.99491
Atom 3 has atomic number 1 and mass 1.00783
Atom 4 has atomic number 1 and mass 1.00783
Atom 5 has atomic number 1 and mass 1.00783
Molecular mass: 49.99215 amu.
Principal axes and moments of inertia in atomic units:
1 2 3
EIGENVALUES -- 15.00642 119.10319 122.63566
X 0.99679 -0.05040 -0.06220
Y 0.04390 0.99385 -0.10169
Z 0.06694 0.09863 0.99287
THIS MOLECULE IS AN ASYMMETRIC TOP.
ROTATIONAL SYMMETRY NUMBER 1.
ROTATIONAL TEMPERATURES (KELVIN) 5.77176 0.72721 0.70627
ROTATIONAL CONSTANTS (GHZ) 120.26460 15.15275 14.71628
1 IMAGINARY FREQUENCIES IGNORED.
Zero-point vibrational energy 80721.9 (Joules/Mol)
19.29299 (Kcal/Mol)
VIBRATIONAL TEMPERATURES: 1070.37 1280.54 1360.85 1447.74 1632.10
(KELVIN) 3281.13 3328.61 6015.76
Zero-point correction= 0.030745 (Hartree/Particle)
Thermal correction to Energy= 0.033834
Thermal correction to Enthalpy= 0.034778
Thermal correction to Gibbs Free Energy= 0.007059
Sum of electronic and zero-point Energies= -418.337510
Sum of electronic and thermal Energies= -418.334422
Sum of electronic and thermal Enthalpies= -418.333477
Sum of electronic and thermal Free Energies= -418.361196
E (Thermal) CV S
KCAL/MOL CAL/MOL-KELVIN CAL/MOL-KELVIN
TOTAL 21.231 8.293 58.339
ELECTRONIC 0.000 0.000 0.000
TRANSLATIONAL 0.889 2.981 37.652
ROTATIONAL 0.889 2.981 20.022
VIBRATIONAL 19.453 2.332 0.666
Q LOG10(Q) LN(Q)
TOTAL BOT 0.566492D-03 -3.246806 -7.476047
TOTAL V=0 0.785178D+11 10.894968 25.086592
VIB (BOT) 0.769348D-14 -14.113877 -32.498404
VIB (V=0) 0.106634D+01 0.027897 0.064236
ELECTRONIC 0.100000D+01 0.000000 0.000000
TRANSLATIONAL 0.138935D+08 7.142813 16.446935
ROTATIONAL 0.529978D+04 3.724258 8.575421
-------------------------------------------------------------------
PH2O
-------------------
- Thermochemistry -
-------------------
Temperature 298.150 Kelvin. Pressure 1.00000 Atm.
Atom 1 has atomic number 15 and mass 30.97376
Atom 2 has atomic number 8 and mass 15.99491
Atom 3 has atomic number 1 and mass 1.00783
Atom 4 has atomic number 1 and mass 1.00783
Molecular mass: 48.98433 amu.
Principal axes and moments of inertia in atomic units:
1 2 3
EIGENVALUES -- 12.64722 126.26481 129.37025
X 0.99885 0.00000 -0.04801
Y 0.00000 1.00000 0.00000
Z 0.04801 0.00000 0.99885
THIS MOLECULE IS AN ASYMMETRIC TOP.
ROTATIONAL SYMMETRY NUMBER 1.
ROTATIONAL TEMPERATURES (KELVIN) 6.84842 0.68597 0.66950
ROTATIONAL CONSTANTS (GHZ) 142.69868 14.29330 13.95020
Zero-point vibrational energy 45593.4 (Joules/Mol)
10.89710 (Kcal/Mol)
WARNING-- EXPLICIT CONSIDERATION OF 1 DEGREES OF FREEDOM AS
VIBRATIONS MAY CAUSE SIGNIFICANT ERROR
VIBRATIONAL TEMPERATURES: 757.72 1097.25 1185.11 1528.96 3179.70
(KELVIN) 3218.46
Zero-point correction= 0.017366 (Hartree/Particle)
Thermal correction to Energy= 0.020594
Thermal correction to Enthalpy= 0.021539
Thermal correction to Gibbs Free Energy= -0.006329
Sum of electronic and zero-point Energies= -417.770092
Sum of electronic and thermal Energies= -417.766863
Sum of electronic and thermal Enthalpies= -417.765919
Sum of electronic and thermal Free Energies= -417.793786
E (Thermal) CV S
KCAL/MOL CAL/MOL-KELVIN CAL/MOL-KELVIN
TOTAL 12.923 8.803 58.651
ELECTRONIC 0.000 0.000 0.000
TRANSLATIONAL 0.889 2.981 37.591
ROTATIONAL 0.889 2.981 19.963
VIBRATIONAL 11.146 2.841 1.097
VIBRATION 1 0.882 1.191 0.595
Q LOG10(Q) LN(Q)
TOTAL BOT 0.814564D+03 2.910925 6.702653
TOTAL V=0 0.791598D+11 10.898505 25.094735
VIB (BOT) 0.117483D-07 -7.930026 -18.259560
VIB (BOT) 1 0.304626D+00 -0.516232 -1.188669
VIB (V=0) 0.114170D+01 0.057553 0.132521
VIB (V=0) 1 0.108549D+01 0.035625 0.082031
ELECTRONIC 0.100000D+01 0.000000 0.000000
TRANSLATIONAL 0.134755D+08 7.129546 16.416387
ROTATIONAL 0.514524D+04 3.711405 8.545826
-------------------------------------------------------------------
PH2
-------------------
- Thermochemistry -
-------------------
Temperature 298.150 Kelvin. Pressure 1.00000 Atm.
Atom 1 has atomic number 15 and mass 30.97376
Atom 2 has atomic number 1 and mass 1.00783
Atom 3 has atomic number 1 and mass 1.00783
Molecular mass: 32.98941 amu.
Principal axes and moments of inertia in atomic units:
1 2 3
EIGENVALUES -- 6.56378 7.87236 14.43614
X 1.00000 -0.00001 0.00000
Y 0.00001 1.00000 0.00000
Z 0.00000 0.00000 1.00000
THIS MOLECULE IS AN ASYMMETRIC TOP.
ROTATIONAL SYMMETRY NUMBER 1.
ROTATIONAL TEMPERATURES (KELVIN) 13.19567 11.00222 5.99977
ROTATIONAL CONSTANTS (GHZ) 274.95472 229.25036 125.01554
Zero-point vibrational energy 34576.8 (Joules/Mol)
8.26404 (Kcal/Mol)
VIBRATIONAL TEMPERATURES: 1633.73 3328.75 3354.73
(KELVIN)
Zero-point correction= 0.013170 (Hartree/Particle)
Thermal correction to Energy= 0.016024
Thermal correction to Enthalpy= 0.016968
Thermal correction to Gibbs Free Energy= -0.007843
Sum of electronic and zero-point Energies= -342.496115
Sum of electronic and thermal Energies= -342.493261
Sum of electronic and thermal Enthalpies= -342.492316
Sum of electronic and thermal Free Energies= -342.517128
E (Thermal) CV S
KCAL/MOL CAL/MOL-KELVIN CAL/MOL-KELVIN
TOTAL 10.055 6.219 52.220
ELECTRONIC 0.000 0.000 1.377
TRANSLATIONAL 0.889 2.981 36.413
ROTATIONAL 0.889 2.981 14.375
VIBRATIONAL 8.278 0.258 0.055
Q LOG10(Q) LN(Q)
TOTAL BOT 0.405074D+04 3.607534 8.306655
TOTAL V=0 0.462470D+10 9.665084 22.254677
VIB (BOT) 0.879585D-06 -6.055722 -13.943815
VIB (V=0) 0.100422D+01 0.001827 0.004207
ELECTRONIC 0.200000D+01 0.301030 0.693147
TRANSLATIONAL 0.744770D+07 6.872022 15.823416
ROTATIONAL 0.309175D+03 2.490204 5.733907
-------------------------------------------------------------------
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