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Chapter

Cover Making the Transition to University Chemistry

Carboxylic Acids and Their Derivatives  

This chapter discusses carboxylic acids and their derivatives. It notes RCOOH as the general formula for carboxylic acids. Thus, the weak acids neutralize alkalis and react with carbonates. Additionally, acyl chlorides typically react with water, alcohols, ammonia, and amines. In esters, the presence of a concentrated sulfuric acid catalyst forms an equilibrium mixture as the option of leaving the tetrahedral intermediate becomes available. On the other hand, acylation reactions are triggered when an acyl group replaces a hydrogen atom in the nucleophile. The chapter also covers the nucleophilic additional-elimination reactions of acid derivatives. It lists the general formula of esters and acyl chlorides as well.

Chapter

Cover Organic Chemistry

Nucleophilic substitution at the carbonyl group  

This chapter describes nucleophilic substitution at the carbonyl group. Most of the starting materials for, and products of, these substitutions will be carboxylic acid derivatives. Acetyl chloride will react with an alcohol in the presence of a base to give an acetate ester. The first step of the reaction is addition of the nucleophilic alcohol to the electrophilic carbonyl group. The base is important because it removes the proton from the alcohol once it attacks the carbonyl group. A base commonly used for this is pyridine. If the electrophile had been an aldehyde or a ketone, we would get an unstable hemiacetal, which would collapse back to starting materials by eliminating the alcohol. With an acyl chloride, the alkoxide intermediate we get is also unstable. It collapses again by an elimination reaction, this time losing chloride ion, to form the ester.

Chapter

Cover Functional Groups

Carboxylic acids and derivatives  

This chapter discusses trends in general reactions, carboxylic acids, acyl chlorides and acid anhydrides, esters, and amides. It reviews the chemistry of carboxylic acids and their derivatives. This is mostly concerned with the attack of nucleophiles. It explains that acids generally do not react in this way because they have an acidic H, but after protonation they are prone to nucleophilic attack. The chapter also demonstrates a general reaction that consists of addition and elimination and refers to a stereoelectronic factor that favours the approach of the nucleophile at 90° to the carbonyl group. The chapter describes methanoic acid as unique in being a reducing agent and the strongest acid. Other acids are resistant to oxidation. It mentions the Schmidt reaction as something that is restricted to acids in which the R group is stable to strong mineral acid.

Chapter

Cover Organic Chemistry

Carbonyl chemistry  

This chapter studies carbonyl chemistry. In its simplest form, the carbonyl group is a carbon to oxygen double bond. A neutral carbon atom must have four bonds, therefore the nature of the other substituents at the central carbon atom will dictate what type of carbonyl group it is and also its reactivity profile. The chapter then looks at reactions with nucleophiles and with reducing agents. There are a range of methods to reduce a carbonyl group, but the simplest ones usually provide a source of hydride that acts as a nucleophile and adds to the central carbon atom. The chapter also considers carboxylic acids, acyl chlorides, esters, and amides.

Chapter

Cover Why chemical reactions happen

Reactions  

This chapter explains the relationship between molecular orbital and chemical reactions. It shows how energies of the orbitals help us understand why the reaction occurs. Knowing the shapes is vital in understanding how the reaction takes place. Moreover, the chapter uses the formation of lithium borohydride to showcase chemical reactions. It notes the nucleophilic addition to a carbonyl group as one of the most significant reactions in organic chemistry. The chapter also analyses nucleophilic attack on carbonyl, carbon–carbon double bond, and acyl chlorides. It then turns to the process of nucleophilic substitution. Finally, the chapter hints at the possibility of a reversible reaction between carboxylic acid and alcohol.

Chapter

Cover Core Carbonyl Chemistry

Reactions of nucleophiles with other carboxylic acid derivatives  

This chapter focuses on reactions of nucleophiles with other carboxylic acid derivatives. The esters which were considered in the previous chapter lie roughly in the middle of a reactivity series in which the ease of nucleophilic attack at the carbonyl carbon decreases from left to right. Thiol esters are between ordinary esters and carboxylic acid anhydrides in reactivity. The carboxylic acids themselves are the least reactive because they are converted to carboxylate complexes on which nucleophilic attack is very difficult. The chapter then looks at amides. Ammonia and amines simply form salts with carboxylic acids, and these are stable except at high temperatures. Acyl chlorides react very easily with ammonia and amines.