  We performed a study of high redshift ($z>2$) quasars, looking for the main
differences between Radio Loud Quasars (RLQ) and Radio Quiet Quasars (RQQ) in
the X-ray band. Our sample of 472 RQQ and 81 RLQ was selected by cross-matching
the SDSS DR7 quasars catalog with the Chandra Source Catalog. We computed the
X-ray luminosity for the two samples and confirmed the X-ray luminosity excess
of RLQ over RQQ. We fit the X-ray spectra assuming the absorbed power law model
and obtained the photon index ($\Gamma$) values for all the sources in the
sample. We excluded quasars with a low number of counts ($<10$) and large
uncertainty on the best-fit photon index ($\Gamma_{err}>1$), and obtained the
mean values of $\Gamma_{RLQ}=1.70 \hspace{0.5mm}_{-0.33}^{+0.36}$ and
$\Gamma_{RQQ}=2.19 \hspace{0.5mm}_{-0.44}^{+0.46}$ for the RLQ and RQQ samples,
respectively, showing that the RLQ have flatter (harder) X-ray spectra than
RQQ. The Kuiper-two test confirms this result with the significant difference
between the RLQ and RQQ photon index distributions ($D_{k}=0.37$ and P-value $=
10^{-6}$). We also evaluated the hardness ratio distributions and confirmed
that the spectra of RLQ are flatter than the spectra of the RQQ. The RLQ's
hard-to-soft ratio distribution is skewed towards the hard X-ray band, while
the RQQ is towards the soft X-ray band. The hard-to-medium and medium-to-soft
ratios show no difference.
