Structural Chemistry

STRUCTURAL CHEMISTRY

SUPPLEMENTARY MATERIAL

associated with the paper

THERMOCHEMICAL AND STRUCTURAL PROPERTIES OF ANTHRAQUINONES

Juan Z. Dávalos · Pilar Jiménez · María Victoria Roux · María Teresa Molina · Tzvetanka Filipova · Errol Lewars · Joel F. Liebman

S1. Combustion calorimetry

The massic energies of combustion of 1,4-anthraquinone (1) were determined by burning the solid samples in pellet form in oxygen inside the micro-bomb. In order to obtain complete reactions of combustion, vaseline was used as auxiliary substance. To verify complete combustion, at the end of each experiment the total quantity of gas in the bomb was slowly released (0.2 cm3 · s-1) through Dräger tubes. No traces of CO were detected. The massic energy of combustion of vaseline used was -(46086 ± 5) J·g-1

[i]. The empirical formula and massic energy of combustion of our cotton-thread fuse,

-1 C1.000H1.740O0.871 and -(17410 ± 37) J·g respectively, were also determined by us.

The nitric acid content in the bomb liquid was determined by titration with 0.1

mol·dm-3 NaOH (aq.). The corrections for nitric acid formation were based on –

-1 ii -3 59.7 kJ·mol [ ] for the molar energy of formation of 0.1 mol·dm HNO3(aq) from

N2, O2 and H2O(l). All the necessary weighing samples were made in a Mettler

UMX2 ultra-micro balance (± 10-7 g) and corrections of apparent mass to mass

were made. For the conversion of the energy of the actual bomb process to that of

the isothermal process, and correction to standard states, we have used the values,

-3 determined in our laboratory, of density  = 1.24 g·cm , massic heat capacity cp =

-1 -1 3 -1 -1 1.07 J·K ·g and (V/T)p was assumed to be 3.56 dm ·g ·K , a value typical for

most of the organic compounds. The corrections to standard states and massic

energy of combustion of the compound studied (referred to T = 298.15 K) were

made according to Hubbard et al [iii]. The atomic weights of the elements were

those recommended by IUPAC in 2005 [iv]. TABLE S1. Results of combustion experiments for 1 at T= 298.15 K,

m (compound)a/mg 50.8313 51.5581 49.9853 50.0020 47.4455 m' (vaseline)a/mg 13.2901 13.0352 11.7555 14.0326 11.4234 m'' (fuse)a/mg 0.5441 0.5794 0.5762 0.5508 0.7378

Tc/K=(Tf-Ti+Tcorr)/K 1.0499 1.0553 1.0036 1.0540 0.9606

b (calor) (-Tc)/J -2202.88 -2214.24 -2105.89 -2211.58 -2015.61

c (cont.) (-Tc)/J -0.99 -0.99 -0.94 -0.99 -0.89

d Uign /J 0.43 0.43 0.43 0.43 0.43

e Udec (HNO3) /J 0.26 0.47 0.35 0.35 0.65 U(corr. to std. states)f/J 1.41 1.43 1.36 1.41 1.29

o -m'cu (vaseline)/J 613.50 600.75 541.78 646.72 526.47

o -m''cu (fuse)/J 9.48 10.10 10.04 9.60 12.86

o -1 cu (compound)/kJ·g -31.0786 -31.0727 -31.0665 -31.0799 -31.0842

o -1 <cu (298.15K)>/ kJ·g -31.0764 ± 0.0031

3 i i For the definition of the symbols see reference [3]. Tth = 298.15 K; Vbomb=0.022 dm ; p gas = 3.04 MPa; m water = 0.05 g. a Corrected masses obtained from weight by calculating the buoyancy; b (calor) is the energy equivalent of the whole system minus the content of the bomb.c (cont.) energy equivalent of the contents of the bomb (cont.) (-

i i f f d e Tc) =  con(T - 298.15K) +  con (298.15K - T + Tcorr.); Experimental energy of ignition; Experimental energy f of formation of HNO3; U(corr. to std. states) is the standard state correction

S2. Knudsen-effusion method

The apparatus consists basically of a stainless steel sublimation chamber

immersed in a thermo-regulated water jacket and connected to a vacuum system (10-4

Pa). The Knudsen cell is weighed before and after each effusion time period, t, to

determine the mass, m, of sublimed material. The weighings were reproducible to within ± 5·10-6 g (Mettler Toledo AT21 balance). The vapour pressure, p, for each

temperature, T, was calculated from the Knudsen equation:

1/2 p = (Δm/Wa at)·(2πRT/M) (S1)

2 where a = (0.669 ± 0.001) mm is the area of the effusion orifice, Wa = (0.986 ± 0.003)

the corresponding Claussing coefficient [v], and M the molar mass of the studied

compound.

TABLE S2. Knudsen effusion results of 1

T/K t/s m/mg p/Pa T/K t/s m/mg p/Pa

373.05 29376 4.03 0.0635 381.59 21900 7.55 0.1615

374.83 24962 4.36 0.0810 382.65 18061 7.80 0.2026

377.08 23864 5.36 0.1046 384.92 9415 4.67 0.2334

379.25 14568 3.94 0.1263 387.20 13188 8.72 0.3120 S3. Computational results

TABLE S3. Computational results for anthraquinones at B3LYP/6-311++G(3df,2p)

level of theory. E0 =Total Energies at 0 K. H298 = Enthalpies and G298 = Gibbs Free

Energies at 298.15 K. All values are given in units of Hartree/particle

Compounds Conf. a E0 G298 H298 Population (Symm.) (%)

1,4-anthraquinone (1) C2v -688.806745 -688.843765 -688.794457

C2h -688.822179 -688.859179 -688.810015 66.8 9,10-anthraquinone (2) D2h -688.822161 -688.858519 -688.809994 33.2

9-hydroxy-1,4- Cs -764.069287 -764.107560 -764.056331 ~100 anthraquinone (3) 3a -764.046056 -764.085533 -764.032446 9-methoxy-1,4- 4 -803.328525 -803.370111 -803.313366 50.7 anthraquinone (4) 4enan -803.328517 -803.370083 -803.313363 49.3 a Obtained from equilibrium constant (molar fraction) K = exp (-G/RT).

References i. Sabbah R, Perez JAG (1997) Thermochim Acta 297: 17-32 ii. Wagman DD, Evans WH, Parker VB, Schumm RH, Halow I, Bailey SM, Churney KL, Nuttall RL (1982) The NBS Tables of Chemical Thermodynamic properties: Selected values for inorganic and C1 and C2 organic substances in SI units, J Phys Chem Ref Data 11: Supplement No 2 iii. Hubbard WN, Scott DW, Waddington G (1967) Rossini FD (ed.) Experimental Thermochemistry, Interscience, New York, 75-128 iv. Wieser M (2006) Pure Appl Chem 78:2051-2066. v. Freeman RD, Searcy AW (1954) J Chem Phys 22:762-763