ALKENES: Summary of electrophilic additions [00:00:40] ALKINES: Halogenation [00:11:00] / Addition of HX [00:13:00] / Addition of water [00:18:00] / Hydrogenation [00:19:50] / Deprotonation and alkylation [00:22:00] AROMATICS: Benzene [00:40:10] / Occurrence in nature [00:44:00] / Hückel's rule [00:47:10] / Heteroaromatics [00:51:20] / Nucleotides [01:06:50] In part 13 of the series "Organic Chemistry" we focus on the reactions of alkynes and on the class of aromatics. To start with, we will summarize the reactions of alkenes: While halogenations are trans-additions, epoxidations and hydrogenations are cis-additions (00:00:40). These transformations are based on the same general mechanism (00:05:00). Reactions of olefins with hydrogen halides and water under Broensted acid catalysts are not stereospecific. The reactivity of alkynes is similar to that of alkenes, but here too electrophilic additions are preferred (00:10:20). Oxidation with halogens yields trans-dihaloalkenes (00:11:00), additions of hydrohalides lead to alkenyl halides (00:13:00). In the presence of an acid as a catalyst, additions of water produce ketones (00:18:00). The Lindlar catalyst enables the synthesis of cis-alkenes under a hydrogen atmosphere (00:19:50). Terminal alkynes have a high CH acidity and can be deprotonated with strong bases to form carbanions (00:22:00). These alkynyl anions are good nucleophiles that can be alkylated with alkyl halides. Alkynes are rarely found in nature; the enediyne antibiotic calicheamicin is an example (00:30:50). Below we will introduce you to an important class of compounds, aromatics (00:39:30). We will first analyze the bonding relationships of these molecules using the example of benzene, a carcinogenic chemical (00:40:10). Aromatics are found in nature in nucleic acids, coenzymes, steroids and amino acids and in urban environments also in coffee (00:44:00). These are cyclic and planar molecules with extended pi systems. Using Hückel's rule, we can determine whether a chemical compound is an aromatic compound (00:47:10). Various aromatic compounds and heteroaromatic compounds are presented below, such as naphthalene (00:49:50), pyridine (00:51:20), pyrimidine (00:59:30), pyrrole (01:08:30), imidazole (01:13:30), furan (01:21:40), thiophene, oxazole and thiazole (01:26:10) and indole (01:28:00). These structures appear in nicotinamide adenine dinucleotide (NAD+), the amino acids histidine and tryptophan and the nucleobases uracil, thymine and cytosine. The furanose isomers of carbohydrates are derived from furan. The nucleobases, in turn, are important building blocks for nucleotides such as ATP, coenzyme A and NAD+ and the human genome DNA (01:06:50). We discuss when free electron pairs of ring heteroatoms are involved in the pi system and when this is not the case (01:11:30). The playlist with all parts of the course and live streams can be found at: • Organic Chemistry A description of the contents of all course parts and the script are available at the following link: https://www.peterhuylab.de/youtube/ The password for the “teaching materials” area with the course script can be obtained from Prof. Huy (peter.huy[at]uni-rostock.de). For this course unit, slides 30 - 36 of “Chapter 6: Chemistry of Alkanes, Alkenes and Alkynes” and 1 - 12 of “Chapter 7: Aromatics” were used. This video is an unedited recording of the live streaming of the lecture “Organic Chemistry for Life Sciences and Biology Teaching” by Prof. Dr. Peter Huy from May 19, 2021 at the Institute of Chemistry at the University of Rostock.