Corrected Text
Slide 1: Aromatic acids
Learning Objectives
At the end of this class session, you will be able to know about
• Preparation and properties of aromatic acids
Slide 2: Introduction
Aromatic carboxylic acids belong to the group of carboxylic acids. Aromatic acids are white crystalline solids that are soluble in hot water, alcohol and ether. It is partially soluble in cold water.
Slide 3: Explanation
Preparation of aromatic acids
Teacher: Hi, students. Today we are going to learn about the preparation of aromatic acids.
Aromatic carboxylic acid is a group of carboxylic acid linked directly to the benzene ring. Benzoic acid is the simplest aromatic acid.
Oxidation of side-chain of benzene derivatives produces aromatic acids. Acid
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Teacher: C6H5MgBr is the formula of Grignard reagent.
Let us see an animation regarding this.
Animation_1_ Preparation of aromatic acids
A carboxylic acid group directly linked to the benzene ring is termed as Aromatic carboxylic acids.
Following figure shows some of the examples of aromatic acids:
Among all the aromatic acids, benzoic acid is the simplest aromatic acid.
Preparation of aromatic acids:
1) By oxidation: Aromatic acids can be obtained by the oxidation of ‘side chain’ of benzene derivatives.
Side chain can be any aliphatic portion linked to benzene ring.
For the process of oxidization of the ‘side chain’, acid dichromate or permanganate or alkaline, permanganate etc., can be used.
Following figure shows the side chains used during oxidization to obtain aromatic acids:
In the process of oxidization of Toluene, acidified KMnO4 is used.
Following reactions show the process of oxidization of Toluene by acidified KMnO4:
2) Hydrolysis of phenyl cyanide:
Following figure shows the procedure to obtain aromatic acid by hydrolysis of phenyl cyanide:
3) Carbonation of Grignard reagent followed by hydrolysis:
Following figure shows the process of carbonation of Grignard reagent followed by
...icted α-methyl-2-naphthalenemethanol. Probably the most obvious clue that corresponded to this secondary alcohol was the seven integrated hydrogens within the aromatic region of 7.5-7.9 ppm. This compound was the only one that had seven hydrogens belonging to naphthalene. The other two secondary alcohols 3-methoxy-α-methylbenzyl alcohol and 4-bromo-α-methylbenzyl alcohol have only four aromatic hydrogens.
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The percent yield of products that was calculated for this reaction was about 81.2%, fairly less pure than the previous product but still decently pure. A carbon NMR and H NMR were produced and used to identify the inequivalent carbons and hydrogens of the product. There were 9 constitutionally inequivalent carbons and potentially 4,5, or 6 constitutionally inequivalent hydrogens. On the H NMR there are 5 peaks, but at a closer inspection of the product, it seems there is only 4 constitutionally inequivalent hydrogens because of the symmetry held by the product and of this H’s. However, expansion of the peaks around the aromatic region on the NMR show 3 peaks, which was suppose to be only 2 peaks. In between the peaks is a peak from the solvent, xylene, that was used, which may account to for this discrepancy in the NMR. Furthermore, the product may have not been fully dissolved or was contaminated, leading to distortion (a splitting) of the peaks. The 2 peaks further down the spectrum were distinguished from two H’s, HF and HE, based off of shielding affects. The HF was closer to the O, so it experienced more of an up field shift than HE. On the C NMR, there are 9 constitutionally inequivalent carbons. A CNMR Peak Position for Typical Functional Group table was consulted to assign the carbons to their corresponding peaks. The carbonyl carbon, C1, is the farthest up field, while the carbons on the benzene ring are in the 120-140 ppm region. The sp3 hybridized carbon, C2 and C3, are the lowest on the spectrum. This reaction verifies the statement, ”Measurements have shown that while naphthalene and benzene both are considered especially stable due to their aromaticity, benzene is significantly more stable than naphthalene.” As seen in the reaction, the benzene ring is left untouched and only the naphthalene is involved in the reaction with maleic
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The final product was p-methoxybenzoic acid and its identity was confirmed by melting point range of 183.6 – 184.8 oC, which closely corresponds to a standard of 185 oC. (Lehman). Since the melting point range is small, it confirms the purity of the product. Since the objective of the experiment was to determine the structure of the major component
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