Context : How complex organic – and potentially prebiotic – molecules are formed in regions of low- and high-mass star-formation remains a central question in astrochemistry .
In particular , with just a few sources studied in detail , it is unclear what role environment plays in complex molecule formation .
In this light , a comparison of relative abundances of related species between sources might be useful to explain observed differences .

Aims : We seek to measure the relative abundance between three important complex organic molecules , ethylene glycol ( ( CH _ { 2 } OH ) _ { 2 } ) , glycolaldehyde ( CH _ { 2 } OHCHO ) and methyl formate ( HCOOCH _ { 3 } ) , toward high-mass protostars and thereby provide additional constraints on their formation pathways .

Methods : We use IRAM 30-m single dish observations of the three species toward two high-mass star-forming regions – W51/e2 and G34.3+0.2 – and report a tentative detection of ( CH _ { 2 } OH ) _ { 2 } toward both sources .

Results : Assuming that ( CH _ { 2 } OH ) _ { 2 } , CH _ { 2 } OHCHO and HCOOCH _ { 3 } spatially coexist , relative abundance ratios , HCOOCH _ { 3 } / ( CH _ { 2 } OH ) _ { 2 } , of 31 and 35 are derived for G34.3+0.2 and W51/e2 , respectively .
CH _ { 2 } OHCHO is not detected , but the data provide lower limits to the HCOOCH _ { 3 } /CH _ { 2 } OHCHO abundance ratios of \geq 193 for G34.3+0.2 and \geq 550 for W51/e2 .
A comparison of these results to measurements from various sources in the literature indicates that the source luminosities may be correlated with the HCOOCH _ { 3 } / ( CH _ { 2 } OH ) _ { 2 } and HCOOCH _ { 3 } /CH _ { 2 } OHCHO ratios .
This apparent correlation may be a consequence of the relative timescales each source spend at different temperatures-ranges in their evolution .
Furthermore , we obtain lower limits to the ratio of ( CH _ { 2 } OH ) _ { 2 } /CH _ { 2 } OHCHO for G34.3+0.2 ( \geq 6 ) and W51/e2 ( \geq 16 ) .
This result confirms that a high ( CH _ { 2 } OH ) _ { 2 } /CH _ { 2 } OHCHO abundance ratio is not a specific property of comets , as previously speculated .

Conclusions :