Amine Structure
Amine structures are organic compounds containing a nitrogen atom bonded to hydrogen atoms and/or alkyl or aryl groups. They are characterized by the presence of a lone pair of electrons on the nitrogen atom, which makes them basic and capable of forming hydrogen bonds. Amines are important building blocks in organic synthesis and are found in many biological molecules.
4 Key excerpts on "Amine Structure"
eBook - ePub- Graham Patrick(Author)
- 2004(Publication Date)
- Taylor & Francis(Publisher)
...If the substituents are all alkyl groups, the amine is defined as being an alkylamine. If there is at least one aryl group directly attached to the nitrogen, then the amine is defined as an arylamine. The nitrogen atom has four sp 3 hybridized orbitals pointing to the corners of a tetrahedron in the same way as an sp 3 hybridized carbon atom. However, one of the sp 3 orbitals is occupied by the nitrogen's lone pair of electrons. This means that the atoms in an amine functional group are pyramidal in shape. The C–N–C bond angles are approximately 109° which is consistent with a tetrahedral nitrogen. However, the bond angle is slightly less than 109° since the lone pair of electrons demands a slightly greater amount of space than a σ bond. Pyramidal inversion Since amines are tetrahedral, they are chiral if they have three different substituents. However, it is not possible to separate the enantiomers of a chiral amine since amines can easily undergo pyramidal inversion — a process which interconverts the enantiomers (Figure 1). The inversion involves a change of hybridization where the nitrogen becomes sp 2 hybridized (Section A4) rather than sp 3 hybridized. As a result, the molecule becomes planar and the lone pair of electrons occupy a p orbital. Once the hybridization reverts back to sp 3, the molecule can either revert back to its original shape or invert. Although the enantiomers of chiral amines cannot be separated, such amines can be alkylated to form quaternary ammonium salts where the enantiomers can be separated. Figure 1. Pyramidal inversion. Once the lone pair of electrons is locked up in a σ bond, pyramidal inversion becomes impossible and the enantiomers can no longer interconvert. Physical properties Amines are polar compounds and intermolecular hydrogen bonding is possible for primary and secondary amines. Therefore, primary and secondary amines have higher boiling points than alkanes of similar molecular weight...
eBook - ePub- Tony Farine, Mark A. Foss(Authors)
- 2013(Publication Date)
- Routledge(Publisher)
...They are formed from a reaction between an alcohol and a carboxylic acid, such as that shown in Figure 3.18. Figure 3.18 The formation of an ester. What type of reaction is this? It is a combination reaction, but since it results in the elimination of water, it is referred to as a condensation reaction. Of course, it is possible for an ester to undergo a decomposition reaction in order to reform a carboxylic acid and an alcohol, but in order for this to take place a water molecule would be required. A decomposition reaction of this type is referred to as hydrolysis – meaning to break with water. Since lipids (fats) are esters, this group of organic compounds will be encountered frequently during your study of health and illness. Lipids are explained in Chapter 7. Figure 3.19 The structural formulae of methyl amine. Amines Figure 3.20 The structural formulae of the amino acid glycine. Amines are organic compounds that possess an amino group (NH 2) and conform to the general formula RCH 2 NH 2. The simplest amine is, therefore, methyl amine, the structural formula of which is given in Figure 3.19. Amino acids, the molecules that join together to form proteins, possess both an amino group and a carboxyl group. Proteins are explained in Chapter 7. The structure of the amino acid glycine is shown in Figure 3.20. Other important molecules that occur in the body and that contain an amino group include the catecholamines epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine. Adrenaline is a hormone and dopamine is a neurotransmitter, while noradrenaline functions in both these roles. The analgesic (pain reliever) morphine and amphetamines are also amines, as their names imply. Aromatic compounds Aromatic hydrocarbons consist of unsaturated molecules in which the carbon atom chain is arranged in a ring, as the example of benzene (C 6 H 6) shows in Figure 3.21...
eBook - ePubBiochemistry Explained
A Practical Guide to Learning Biochemistry
- Thomas Millar(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...4 Amino Acids and their Functions In this chapter you will learn: the functional groups: an amine and carboxyl groups to understand the general structure of amino acid the structures, names and single letter symbols for the 20 amino acids found in proteins how 2 cysteines may be oxidised to form the bridging amino acid cystine how the carbons of amino acids are named or numbered the terms ampholyte and zwitterion and how these relate to amino acids the structure of an amide bond and the special case a peptide bond special functions of amino acids (e.g. neurotransmitters) and structural relationships between amino acids how ketones are formed from amino acids by removing ammonia from the αC the synthesis of the bioactive amines dopamine, noradrenaline, adrenaline and serotonin. to understand the basis for Parkinson’s disease and phenylketonuria that tyrosine, serine and threonine are phosphorylation sites in proteins the importance of decarboxylation in the formation of some active amines such as histamine how sugars may attach to the amino acids serine, threonine and asparagine Basic structure and nomencalture of amino acids The name amino acid suggests that these structures have an amine and an acid group. Indeed this is true; amino acids have an amino group and a carboxylic acid. The structure of a typical L-amino acid is illustrated below. This type of amino acid is the basis of proteins. Q&A 1 : Draw the chemical structures of a carboxylic acid, and an amine group. There is a central carbon that has bonds to an amine group, a carboxylic acid, an hydrogen and a variable R group. Since this central carbon has 4 different groups attached to it, it is a chiral carbon and hence there are 2 possible isomers, L and D. Nearly all amino acids in biochemistry are of the L-form (L for life). Note that this is the opposite of sugars, which nearly always occur as the D isomer. You need to learn their structure in this orientation...
eBook - ePubBiochemistry
An Organic Chemistry Approach
- Michael B. Smith(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...11 Amino Acids There is an important class of difunctional molecule that is critical to an understanding of biological processes. Amino acids comprise the backbone of peptides, and thereby of enzymes. This chapter will discuss the structure, nomenclature, and characteristics of amino acids. 11.1 Characteristics of Amino Acids An amino acid, as the name implies, has one amine unit (–NR 2) and one carboxylic acid unit (a carboxyl group, COOH). The nomenclature for a generic amino acid is dominated by the carboxyl, so the parent name is “acid” and the NR 2 unit is treated as a substituent. When an amine unit is a substituent the name “amino” is used, so these compounds are amino carboxylic acids, or just amino acids. Amino acids are easily named using IUPAC nomenclature and the carboxylic acid is the parent for each new compound. Two examples are 2-aminopropanoic acid (known as alanine) and 5-amino-3,5-dimethylheptanoic acid. There are a variety of structural variations for amino acids. If the amine unit is attached to C2, the α-carbon of the carboxylic acid chain, the compound is an α-amino acid. If the amine group is on C3, the β-carbon it is a β-amino acid. Similarly, there are γ-amino acids, δ-amino acids, and so on. Due to their biological importance, α-amino acids will be discussed most of the time. The common names of α-amino acids are presented in Table 11.1 in Section 11.2. To distinguish α-amino acids from other amino acids, the term non-α-amino acids is used. 5-Amino-3,5-dimethylheptanoic acid is a non-α-amino acid, for example. Table 11.1 Structures, Names, Three-Letter Code and One-Letter Code of the 20 Essential Amino Acids, Based on the Structure in Figure 11.5 R Name Three-Letter Code One-Letter...
