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Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

\begin{align} \Delta_\mathrm{f} H^\circ (\ce{PhCH2+}) &= \pu{+219 kcal mol-1} \\ \Delta_\mathrm{f} H^\circ (\ce{t-C4H9+}) &= \pu{+169 kcal mol-1} \end{align}

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc [1]., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Addendum

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along with other radicals and cations. I thank G. B. Ellison, University of Colorado, for these data.enter image description here

\begin{array}{llcclc} \hline & \text{Radical} & \Delta_\mathrm{f} H_{298} (\pu{kcal mol-1}) & \qquad & \text{Cation} & \Delta_\mathrm{f} H_{298} (\pu{kcal mol-1}) \\ \hline \text{methyl} & \ce{CH3} & 35.06 \pm 0.07 & & \ce{CH3+} & 261.9 \pm 0.1 \\ \text{$t$-butyl} & \ce{C(CH3)3} & 11.9 \pm 0.2 & & \color{red}{\ce{C(CH3)3+}} & \color{red}{166.4 \pm 0.7} \\ \text{benzyl} & \ce{C6H5CH2} & 50.5 \pm 0.2 & & \color{red}{\ce{C6H5CH2+}} & \color{red}{217.6 \pm 0.2} \\ \text{tropyl} & \ce{C7H7} & 66.5 \pm 0.3 & & \ce{C7H7+} & 210.0 \pm 0.3 \\ \hline \end{array}

Reference

  1. Jo Anne A. Jackson, S. G. Lias, P. Ausloos, J. Am. Chem. Soc., 1977, 99 (23), pp. 7515–7521. DOI: 10.1021/ja00465a020.

Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along with other radicals and cations. I thank G. B. Ellison, University of Colorado, for these data.enter image description here

Gas phase measurements give:

\begin{align} \Delta_\mathrm{f} H^\circ (\ce{PhCH2+}) &= \pu{+219 kcal mol-1} \\ \Delta_\mathrm{f} H^\circ (\ce{t-C4H9+}) &= \pu{+169 kcal mol-1} \end{align}

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase [1].

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along with other radicals and cations. I thank G. B. Ellison, University of Colorado, for these data.

\begin{array}{llcclc} \hline & \text{Radical} & \Delta_\mathrm{f} H_{298} (\pu{kcal mol-1}) & \qquad & \text{Cation} & \Delta_\mathrm{f} H_{298} (\pu{kcal mol-1}) \\ \hline \text{methyl} & \ce{CH3} & 35.06 \pm 0.07 & & \ce{CH3+} & 261.9 \pm 0.1 \\ \text{$t$-butyl} & \ce{C(CH3)3} & 11.9 \pm 0.2 & & \color{red}{\ce{C(CH3)3+}} & \color{red}{166.4 \pm 0.7} \\ \text{benzyl} & \ce{C6H5CH2} & 50.5 \pm 0.2 & & \color{red}{\ce{C6H5CH2+}} & \color{red}{217.6 \pm 0.2} \\ \text{tropyl} & \ce{C7H7} & 66.5 \pm 0.3 & & \ce{C7H7+} & 210.0 \pm 0.3 \\ \hline \end{array}

Reference

  1. Jo Anne A. Jackson, S. G. Lias, P. Ausloos, J. Am. Chem. Soc., 1977, 99 (23), pp. 7515–7521. DOI: 10.1021/ja00465a020.
3 added "with"
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Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along with other radicals and cations. I thank G. B. Ellison, University of Colorado, for these data.enter image description here

Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along other radicals and cations. I thank G. B. Ellison, University of Colorado for these data.enter image description here

Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along with other radicals and cations. I thank G. B. Ellison, University of Colorado, for these data.enter image description here

2 added 295 characters in body
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Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along other radicals and cations. I thank G. B. Ellison, University of Colorado for these data.enter image description here

Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Gas phase measurements give:
PhCH2+: ΔHfo= +219 Kcal/mol
t-C4H9+: ΔHfo= +169 Kcal/mol

The tertiary-butyl cation is seemingly more stable than the benzyl cation in the gas phase. These data do not speak to the condensed phase.

Jo Anne A. Jackson, S. G. Lias, P. Ausloos J. Am. Chem. Soc., 1977, 99 (23), pp 7515–7521 DOI: 10.1021/ja00465a020

Addendum (12/14/2017): The latest data for the gas phase heats of formation of these two cations is here along other radicals and cations. I thank G. B. Ellison, University of Colorado for these data.enter image description here

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