Give diagrammatic representation of
triglyceride
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Explanation:
resources available in large quantities and are predominantly mixtures of triglyceride molecules, which have the three-armed star structure shown in Figure 1. Triglycerides are made up of three fatty acids joined at a glycerol junction. Most of the common oils contain fatty acids that vary from 12 to 22 carbons in length, with 0 to 3 double bonds per fatty acid. The use of vegetable oils as a starting material offers numerous advantages: for example, low toxicity, inherent biodegradability, and high purity [2,3], thus they are considered to be one of the most important classes of renewable resources for the production of biobased polymers [4 – 8]. Polyurethanes (PUs) are one of the most important and versatile classes of polymers and can vary from thermoplastic to thermosetting materials. The industrial production of PUs is normally accomplished through the polyaddition reaction between organic isocyanates and compounds containing active hydroxyl groups, such as polyols. Usually, both isocyanate and polyol are petroleum based. Due to uncertainty about the future cost of petroleum, as well as the desire to move toward more environmentally friendly feedstocks, many recent efforts have focused on replacing all or part of the conventional petroleum-based polyols with those made from vegetable oils. Combined with isocyanates, vegetable oil-based polyols produce PUs that can compete in many ways with PUs derived from petrochemical polyols [9]. Moreover, due to the hydrophobic nature of triglycerides, vegetable oil-based polyols produce PUs that have excellent chemical and physical properties, such as enhanced hydrolytic and thermal stability [9]. The preparation of polyols from vegetable oils for general polyurethane use has been the subject of many studies. For natural oils and derivatives to be used as raw materials for polyol production, multiple hydroxyl functionality is required. Traditionally, plant oil-based polyols have been prepared starting from triglyceride molecules. These polyols have been successfully prepared using different methods; most common is the epoxidation of carbon-carbon double bonds and further oxirane ring-opening with alcohols or other nucleophiles [10 – 16]. Other methodologies involve the transesterification with multifunctional alcohols [17 – 21] and the combination of hydroformylation or ozonolysis and subsequent reduction of carbonyl groups [22 – 30]. Unfortunately, limited attention has been paid to the preparation of diols and polyols from fatty acids, which can be easily isolated from oils [31,32]. In this context, our research is focused in the preparation of diols and polyols from oleic acid (OL) and undecylenic acid (UD). OL is a C18 fatty acid containing a carbon-carbon double bond at the ninth position that can be found in several natural oils such as olive oil (71%), canola oil (61%), sunflower oil (42%) and palm oil (39%). Modern genetic engineering techniques are already able to develop natural oils with much higher content of an individual fatty acid. For example , ―high oleic‖ sunflower oil with an oleic acid content of more than 90% is available. UD is a C11 ...
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