Indian Journal of Chemistry Vol. 59B, January 2020, pp. 126-134 Esters of petroselinic acid containing Trachyspermum copticum seed oil: Potential industrial lubricant base stocks P G Prabhakara Rao* a , K Kamalakar b , T Jyothirmayi a , M S L Karuna b & R B N Prasad b a Resource Centre, Hyderabad, CSIR-Central Food Technological Research Institute, Habshiguda, Uppal Road, Hyderabad 500 007, India b Centre for Lipid Research, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500 007, India E-mail: rao.pamidighantam@gmail.com Received 2 August 2018; accepted (revised) 26 July 2019 Trachyspermum copticum seed oil contains volatile oil rich in thymol, which is distilled out and used for medicinal and aromatic formulations. The seed powder after removal of the volatiles loses its importance. However, the fixed oil being rich in unsaturation with petroselinic acid (18:1, Δ6; 68.3%) and linoleic acid (18:2; 25.3%) is used for preparing biolubricant base stocks. Methyl, isopropyl and 2-ethyl hexyl esters of the oil have been converted to epoxides, followed by in situ hydroxylation and acylation using hexanoic and butyric anhydrides. The acylated products have been evaluated for lubricant properties, and are found to exhibit density (0.91-0.97 g/cc); viscosity of 23.5-27.3 cSt at 40°C and 4.85-5.33 cSt at 100°C. The values are comparable to jatropha acylated products. The products exhibited good copper corrosion resistance value of ‘1a’ and high flash points of 230-242°C. The acylated esters with good weld load behavior, and lower wear and pour point values and viscosity indices, 128.84-138.94, can be potential base stocks belonging to group III category lubricants with ISO VG Grade about 22. These products can be further explored for the preparation of hydraulic, metal working and other industrial fluid formulations. Keywords: Trachyspermum copticum, seed oil, acylated products, biolubricant base stocks Worldwide vegetable oils production is estimated to be 125 MMTs, and it is expected to reach 175 MMTs by 2020. Olive oil based lubricants have been used as early as 1650 BC. Lubricant formulations prepared from vegetable oils namely olive, rapeseed, castor, palm and the animal fats from the sperm whale, lard, and grease from wools were known since 50 AD (Emmanuel et al. 2009; Honary, 2004) 1,2 . Vegetable oils are being investigated as a potential source of environment-friendly lubricants due to their biodegradability, renewability and excellent lubrication properties. A large number of vegetable oils were screened for their potentiality for industrial applications like biodiesel, lubricants, foaming agents and other minor uses, apart from their traditional food applications. Vegetable oils with superior lubricity and emulsifying characteristics enhance their potentiality as additives and compete with the cheaper mineral oil-based lubricants (Honary, 2004) 2 . Masjuki et al. (1999) 3 reported that palm oil-based lubricants reduced the hydrocarbon and carbon monoxide emission levels to a greater extent than mineral oil- based lubricants. The disadvantages like lower oxidative stability and pour points of vegetable oils can be overcome by chemical modifications such as epoxidation, hydroxylation, acetylation at the double bond position, estolide formation, and transesterification of plant oils with polyols, and preparation of acyloxy oils/derivatives (Sharma et al. 2006) 4 . Incorporation of antioxidants, detergents, dispersants, viscosity modifiers, pour point depressants, antiwear agents, rust and corrosion inhibitors, emulsifiers, foam inhibitors, thickeners, friction modifiers, dyes, and biocides into base fluid help in improving their lubricant performance (Rafael et al. 2011) 5 . Formation of epoxide on the double bond is an addition reaction, which can be useful for further conversion to various compounds by reaction with a variety of nucleophiles (Campanella et al. 2008) 6 . Epoxidation reactions have been carried out industrially to obtain a variety of commercially important products. Epoxidation of unsaturated fatty acids of soybean (Sinadinovie-Fiser et al. 2001; Vlcek and Petrovie, 2006) 7,8 and other plant oils like canola (Mungroo et al. 2008) 9 , rapeseed (Milchert et al.