Supplementary Material

MANUSCRIPT TITLE:UV-spectroscopy, electronic structure and ozonolysis reactivity of sesquiterpenes: a theoretical study

AUTHORS:Shu-Xian Hu, Jian-Guo Yu, andEddy Y. Zeng

ADDRESS:State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; College of Chemistry, Beijing Normal University, Beijing 100875, China; and Graduate School, Chinese Academy of Sciences, Beijing 100049, China

NO. of Pages:8

No. OF FIGURES:4

NO. OF TABLES:2

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Comparison of the results from the present study using conceptual DFT and from the literature

By now, quite a few studies employing conceptual DFT to predict the reactivity and stability of compounds have been conducted. To examine the efficiencyof conceptual DFT on computational predictions, the relative enthalpies of formation(ΔHrel), in addition to rate constants (k) of sesquiterpene isomers, were referenced to comparison with chemical hardness (η) in our work (Table S2).

First, isomers with larger ΔHrel have weaker stability and stronger reactive ability than isomers with smaller ΔHrelvalue. It is obvious that congeners with endocyclic C=C bond possess higher chemical reactivity than isomers with an exocyclic C=C bond within a pair of isomers with the same basic structural skeletons. For example,ΔHrelsof4-aromadendrene and longifoleneare 33.2 and 14.4 kcal/mol larger than their corresponding exo isomers, respectively.

Furthermore, in the ozonolysis reaction of sesquiterpenes, isomers with high reactivity present large k. It is evident thatα-humulene with three unsaturated bondsis morereactive in the reaction with OH radicals thanisomers with one or two unsaturated bonds. This result is consistent with our conclusion from conceptual DFT.

In fact, some predictions are not consistent with previously obtained results in the literature. There are three causes. First, a standard enthalpy of formationexhibits the capacity of formation of a sesquiterpene isomer under ideal conditions, rather than its chemical reactivity in ozonolysis reaction. Second, the small difference in reactivity and stability between isomers leads to similar rate constants. Besides, our theoretical predictions are worth notice and further experimental verification.

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TableS1 The first six excitation energy (eV) of sesquiterpenes at the CIS/6-31G(d,p) level

SpeciesEt1Et2Et3Et4Et5Et6

Longicyclene10.5110.6911.0311.1411.2811.37

4-Aromadendrene7.288.729.429.709.9710.13

10-Aromadendrene7.989.359.679.8210.0310.18

α-Patchoulene7.539.099.319.669.9010.41

β-Patchoulene7.349.279.289.4810.1510.28

α-Cedrene7.669.239.499.7510.4510.49

β-Cedrene7.999.219.739.8810.1110.78

α-Cubebene7.339.289.539.789.9110.01

β-Cubebene7.719.219.599.729.7710.14

Longifolene7.798.759.559.749.9910.62

Alloisolongifolene7.989.279.799.9310.1510.68

α-Panasinsanene7.739.169.419.5410.1110.30

β-Panasinsanene7.889.129.629.8810.1710.65

Sativene7.878.779.649.8310.0810.75

Clovene7.909.429.619.7210.5510.66

α-Copaene7.399.039.419.5210.3410.54

Thujepsene7.449.029.409.5210.0310.32

α-cis-Bergamotene7.407.979.059.409.429.52

Sesquicarene7.957.999.389.399.709.77

β-Selinene8.098.179.259.449.839.84

β-Caryophyllene7.707.899.179.339.449.53

Isocaryophyllene7.337.768.929.129.299.37

Guaiadiene7.278.248.659.279.379.51

α-Cadinene7.647.839.289.289.469.54

β-Cadinene7.688.049.289.399.509.61

α-Humulene7.227.797.838.528.969.14

Bisabolene7.477.948.089.079.109.26

α-Zingiberene5.607.918.418.658.748.87

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TableS2 The first six excitation energy (eV) of sesquiterpenes at the CIS/6-31G(d,p) level

SpeciesηaΔHrelb1011×kc

4-Aromadendrene 6.39 80.3 ―

10-Aromadendrene 6.99 47.1 ―

α-Cedrene 6.88 48.9 6.7 ± 1.4

β-Caryophyllene 7.05 161.0 20+5-9

α-Copaene 6.67 ― 9.0±1.9

Alloisolongifolene 7.1 68.4 ―

Longifolene 6.88 82.8 4.7±1.0

α-Humulene 6.39 76.5 29+7-10

a Unit in Hartree.

b Relative stability data, ΔHrel (kJ/mol) =(Hi-HSativene),from Ref 17.

cRate constants data for the gas phase reactions of OH radicalswith a series of sesquiterpenes at 296±2 K from Ref 9.

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Figure S1. Calculated UV spectrum of longicyclene at the CIS/6-31G (d,p) level.

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Figure S2. Calculated UV spectra of unsaturated sesquiterpenes with one double bond at the CIS/6-31G (d,p) level.

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Figure S3. Calculated UV spectra of unsaturated sesquiterpenes with two double bonds at the CIS/6-31G (d,p) level.

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Figure S4. Calculated UV-Vis spectra of unsaturated sesquiterpenes with three double bonds at the CIS/6-31G (d,p) level.

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