Synthesis, Characterization and End Use Evaluation of 2-Allyl-3(5)-Pentadecyl Phenol and their Acrylic/Methacrylic Esters

Fur. Polym.J. Vol. 29, No. 6, pp. 863-869, 1993 0014-3057/93 $6.00 + 0.00 Pergamon Press Ltd Printed in Great Britain. SYNTHESIS, CHARACTERIZATION AND END USE EVALUATION OF 2-ALLYL-3(5)-PENTADECYL PHENOL AND THEIR ACRYLIC/METHACRYLIC ESTERS J. N. RUPAVANI,V. VIJAYALAKSHMI, S. SITARAMAM a n d N. KRISHNAMURTI* B. Organic Coatings and Polymers Division, Indian Institute of Chemical Technology, Hyderabad 500007, India (Received 24 July 1992) Abstract--2-Allyl-3(5)-pentadecyl phenols were synthesized and characterized spectroscopically; their acrylic and methacrylic esters were synthesized. The acrylic ester was evaluated as a reactive monomer in u.v.-curable coating compositions and the methacrylic ester in anaerobic adhesive formulations. Phenolic resin from 2-allyl-3(5)-pcntadecyl phenol was prepared and evaluated as a wood bonding adhesive. INTRODUCTION C a s h e w n u t shell liquid ( C N S L ) is isolated from the pyrolysis o f cashew kernels. This corrosive liquid is used extensively in the m a n u f a c t u r e o f a variety o f phenolic resins required for surface coatings, friction resistance c o m p o n e n t s , laminates, m o u l d i n g materials a n d adhesives [1]. C a r d a n o l , the m a j o r comp o n e n t ( > 9 5 % ) o f double-distilled C N S L [2] can be conveniently h y d r o g e n a t e d [3, 4] to o b t a i n crystalline 3-pentadecyl phenol, which has n o n e o f the vesicant action o f the p a r e n t c o m p o u n d . A n a t t e m p t has n o w been m a d e to synthesize value-added p r o d u c t s derived from allylated pentadecyl phenol, with a view to m a k i n g low molecular weight phenolic resins suitable for w o o d laminates. Acrylic a n d methacrylic esters o f the allylated 3-pentadecyl p h e n o l have also been synthesized a n d evaluated in u.v.-curable coatings a n d a n a e r o b i c adhesive c o m p o s i t i o n s respectively. EXPERIMENTAL PROCEDURES (a) Synthesis of 3-pentadecyl phenol (1) Double-distilled Cardanol was hydrogenated in a Parr medium pressure hydrogenator by a procedure reported earlier [4] using 2% Raney Nickel Catalyst at 150° and 150psi for 4hr. The completely hydrogenated product was freed from catalyst by hot filtration and subsequent distillation under reduced pressure (198-200°/1-2 mm Hg). The product was further purified by crystallization from n-hexane to obtain ( > 95% HPLC) pure 3-pentadecyl phenol (m.p. 51°). (b) Synthesis of 2-allyl-3(5)-pentadecylphenol and 2-propyl3(5)-pentadecyl phenols (Scheme 1) Synthesis of allyl-3-pentadecyl phenyl ether (2). Into a flask, fitted with reflux condenser, a dropping funnel with pressure equalizer and a sealed mechanical stirrer, was placed crystalline 1 (30 g, 0.099 mol) dissolved in 300 ml of dry acetone. Anhydrous potassium carbonate (96.6g, 0.7 mol) was added with stirring. Then there was dropwise *To whom all correspondence should be addressed. addition of allyl bromide (12.1 g, 0.1 mol) over a period of 1.5 hr. The temperature of the reaction mixture was then raised from 30 to 55°, to allow reflux with stirring for 12 hr. Then distilled water (200 ml) was added to the flask. The aqueous layer was extracted with ether (3 x 30 ml). The extracts were combined, washed free of inorganic impurities and dried over Na2SO4. Ether was removed at low pressure to eliminate unreacted allyl bromide. The product thus obtained in liquid form was purified by column chromatography using 2% ethyl acetate in n-hexane as eluent, to eliminate the unreacted starting compound. The physical properties and spectral data are as follows: Yield: 83.0; viscosity: 0.7 poise. i.r. (em-I): 3080-2840, 1650 (>C----C