Naming and Drawing Carboxylic Acids

Transcription

1 Assignment 4 Task 5 Due: 11:59pm on Friday, October 5, 2018 You will receive no credit for items you complete after the assignment is due. Grading Policy Naming and Drawing Carboxylic Acids Aromatic carboxylic acids, like the ones shown below, are named using the common name, benzoic acid, instead of the IUPAC name. On the other hand, alkyl carboxylic acids are typically named using IUPAC guidelines. Part A Using IUPAC guidelines, enter the name for the carboxylic acid shown below. Enter the name using IUPAC guidelines, including numbers and punctuation (e.g., 3,4-dichlorobenzoic acid). Hint 1. How to approach the problem 1. Identify the longest carbon chain containing the carboxyl group, and replace the e in the alkane name with oic acid. 2. Number the carbon chain, beginning with the carboxyl carbon as carbon #1. 3. Name and number any substituents, listing them alphabetically. Hint 2. Identify the longest carbon chain Identify the carbon atoms of the longest carbon chain containing the carboxyl group. Identify the longest carbon chain by selecting each atom individually on the canvas and assigning them a map number of 1 until all atoms are mapped. To do this, right-click on an atom and choose Atom Properties. (Mac users: Use an equivalent for right-clicking.) Then, clear the check mark to enable the Map field before entering a value. 1/9

2 Hint 3. Determine the name of the alkane chain In the molecule, the longest carbon chain that contains the carboxyl group has six carbon atoms. What is the alkane name of a 6-carbon-atom chain? Enter the name of the alkane. hexane Hint 4. Determine the name and number of the substituents In an alkyl carboxylic acid, the carbon atoms are numbered beginning with the carboxyl carbon as number one. The number of the carbon atom that the substituent is bonded to is the number of the substituent. Select the correct name to precede the alkane name. Hint 1. How to name substituents The names of the substituents are modified depending on the type of substituent. If the substituent is a halide, the ine in the element name is replaced with o. If the substituent is a carbon chain, the e in the alkane name is replaced with yl. If the substituent is some other functional group, the name is the name of the functional group. For example, an OH is named hydroxyl. If there is more than one substituent, the substituents are listed alphabetically before the alkane name, with a dash between the substituents (e.g., 3-fluoro-3-methylbutanoic acid). 4-ethyl-3-chloro 3-chloro-2-ethyl 2-methyl-4-chloro 2-ethyl-3-chloro 4-methyl-3-chloro 3-chloro-4-methyl 4-chloro-2-methyl 3-chloro-4-ethyl 2/9

3 3-chloro-4-methylhexanoic acid Part B Draw 3-methylbenzoic acid. Draw the molecule on the canvas by choosing buttons from the Tools (for bonds), Atoms, and Advanced Template toolbars. The single bond is active by default. Hint 1. How to approach the problem 1. Draw the structure of benzoic acid. 2. Number the carbon atoms, starting with the carboxyl group and going around the ring. 3. Add any substituents to the appropriate carbon atoms. Hint 2. Draw benzoic acid Benzene is a 6-carbon-atom ring with one hydrogen atom bonded to each carbon atom. Alternating single bonds and double bonds are drawn between the carbon atoms of the benzene ring to illustrate the equal sharing of electrons between carbon atoms. Benzoic acid is the common name for a carboxyl group attached to a benzene ring. Draw benzoic acid below. Draw the molecule on the canvas by choosing buttons from the Tools (for bonds), Atoms, and Advanced Template toolbars. The single bond is active by default. Hint 3. Determine where the methyl group is attached Identify the carbon atom in benzoic acid to which the methyl group is attached in 3-methylbenzoic acid. Identify the carbon atom by selecting the atom and assigning it a map number of 1. To do this, right-click on an atom and choose Atom Properties. (Mac users: Use an equivalent for right-clicking.) Then, clear the check mark to enable the Map field before entering a value. 3/9

4 Chapter 20 Reading Quiz Question 3 Part A Which carboxylate ion is the most basic? 4/9

5 Hint 1. Basicity of carboxylate ions The basicity of a carboxylate ion is inversely related to the stability of its negative charge. For aromatic carboxylic acids, the electronic effects of substituents can also be conveniently related to the influence of those substituents on electrophilic aromatic substitution reactions. See A B C D Properties of Carboxylic Acids Since carboxylic acids can form hydrogen bonds to create dimers, they have higher boiling points than alcohols and other carbonyl compounds. Carboxylic acids with four or fewer carbon atoms are soluble in water and undergo ionization. As weak acids, carboxylic acids will react with strong bases, such as KOH and NaOH, to form a carboxylate anion. Part A The following compounds have approximately the same molar mass. Rank them based on their boiling points. Rank from highest to lowest boiling point. To rank items as equivalent, overlap them. Hint 1. How to approach the problem When comparing compounds of approximately the same molar mass, the major determining factor for the boiling point is the strength of attractive forces. The strongest attractive force between molecules is hydrogen bonding. Both carboxylic acids and alcohols can form hydrogen bonds, and aldehydes and ketones cannot. However, when carboxylic acids form hydrogen bonds, they create dimers, so the mass is effectively doubled. Greater molar mass leads to a higher boiling point. Hint 2. Classify the compounds Classify each compound as carboxylic acid, alcohol, or ketone. Drag each item to the appropriate bin. 5/9

6 Reset Help Carboxylic acid Alcohol Ketone Reset Help Highest boiling point Lowest boiling point The correct ranking cannot be determined. Part B Sort these carboxylic acids based on their solubility in water. Drag each item to the appropriate bin. Hint 1. Determine what makes a carboxylic acid soluble in water Select the statement below that correctly defines what makes a carboxylic acid soluble in water. If the total number of carbon atoms is four or less, the carboxylic acid is soluble. If the carboxylic acid has five carbon atoms or more, it is soluble. 6/9

7 Reset Help Soluble Not very soluble Part C propanoic acid + strong base Draw the resulting carboxylate anion that forms when propanoic acid reacts with a strong base. Draw the molecule on the canvas by choosing buttons from the Tools (for bonds), Atoms, and Advanced Template toolbars. The single bond is active by default. Include all hydrogen atoms and charges where appropriate. Hint 1. Select the structure of propanoic acid Select the structure of the reactant, propanoic acid, from the possibilities below. 7/9

8 Hint 2. Select the acidic hydrogen atom To act as an acid, a molecule must donate an H + ion. Identify which hydrogen atom is most likely to be removed from propanoic acid as an H + ion. Identify the hydrogen atom by selecting the atom and assigning it a map number of 1. To do this, right-click on an atom and choose Atom Properties. (Mac users: Use an equivalent for right-clicking.) Then, clear the check mark to enable the Map field before entering a value. 8/9

9 Score Summary: Your score on this assignment is 100%. You received 3 out of a possible total of 3 points. 9/9