Nucleophilic addition reactions were described in general terms in Chapter 18. design a multi‑step synthesis in which you may have to use any of the reactions discussed in this chapter together with any number of reactions from previous chapters. 18.5: Nucleophilic Addition Reactions of Ketones and Aldehydes, [ "article:topic", "showtoc:no", "transcluded:yes", "source-chem-45595" ], 18.4: 19.4 New Synthesis of Aldehydes and Ketones, 18.6: Nucleophilic Addition of Water (Hydration), Relative Reactivity of Carbonyl Compounds to Nucleophilic Addition. Recall that bond polarity can be depicted with a dipole arrow, or by showing the oxygen as holding a partial negative charge and the carbonyl carbon a partial positive charge. The carbon-oxygen double bond is polar: oxygen is more electronegative than carbon, so electron density is higher on the oxygen side of the bond and lower on the carbon side. All materials on the site are licensed Creative Commons Attribution-Sharealike 3.0 Unported CC BY-SA 3.0 & GNU Free Documentation License (GFDL). Facts and a simplified mechanism for the reduction of aldehydes and ketones using sodium tetrahydridoborate, NaBH 4. Among these functional groups, ketones and aldehydes are known to be two of the most important functional groups. Many of these reactions are important to chemists concerned primarily with the synthesis of new organic compounds. Aldehydes and ketones undergo nucleophilic addition reactions with monohydric alcohols to yield hemiacetals. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. In each of the following reactions, the general reaction mechanism is the same: nucleophilic addition to a carbonyl. After the carbonyl has reacted with the nucleophile, the negatively charged oxygen has the capacity to act as a nucleophile. The nucleophile can be charged or neutral. Before we consider in detail the reactivity of aldehydes and ketones, we need to look back and remind ourselves of what the bonding picture looks like in a carbonyl. A closer look at the tetrahedral intermediate shows us that if the carbonyl reforms, then the original aldehyde or ketone is reformed. Nucleophilic Addition Reactions of Aldehydes and Ketones Nucleophific addition reactions to the carbon-oxygen double bond. In Chapter 19, we take a more detailed look at these reactions as we make a comprehensive study of the chemistry of aldehydes and ketones. Very often a general acid group serves this purpose, donating a proton to the carbonyl oxygen. tetrahedral complex formation between 2-butanone and cyanide. Have questions or comments? You will notice that a number of these reactions have already appeared in previous units. 19: Aldehydes and Ketones- Nucleophilic Addition Reactions, 18.S: Ethers and Epoxides; Thiols and Sulfides (Summary). Go to menu of other types of mechanism. fulfill all of the detailed objectives listed under each individual section. Ketones and Aldehydes: Nucleophilic Addition Reaction and Imine Enamines It is important to understand how the different functional groups react with each other in the synthesis.
Watch the recordings here on Youtube! . Because the oxygen end of the carbonyl double bond bears a partial negative charge, anything that can help to stabilize this charge by accepting some of the electron density will increase the bond’s polarity and make the carbon more electrophilic. Note that an important differences between aldehydes and ketones is the resistance of the latter to oxidation.