CHMY 162 Lab 3 Alc etc new PDF

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Name: __________________________ CHMY 162 Pre-Lab 3 Reactions of Alcohols, Phenols, Aldehydes, and Ketones WARNING: The pre-lab questions are due at the beginning of the lab. You will not be permitted to stay in the lab if this sheet is not completed. Use the rules to predict the outcomes of these physical and chemical tests for the alcohols, phenols, aldehydes, and ketones. You may need to do some research to find all the answers for these compounds. If no reaction is expected, write NR. Chemical Reactions of Alcohols and phenols: Ethanol 2-Propanol

t-Butyl alc.

Cyclohexanol

o-Cresol

Draw the structure of each compound. Label each as 1o, 2o, 3o, or aromatic.

Predict the color changes for the chromic acid test Predict the expected aqueous solubility from the structure.

Chemical reactions of Aldehydes and Ketones: Propanal Benzaldehyde Draw the structure of each compound

Predict the aqueous solubility from the structure. 2. Iodoform test: Color change 3. Benedict’s test: Color change

Propanone (acetone)

Cyclohexanone

Name: _________________________ Lab 3

CHMY 162

Reactions of : Alcohols, Phenols, Aldehydes, and Ketones

Goal: Learn the naming, structure, physical properties, and chemical reactions of alcohols, phenols, aldehydes, and ketones. Identify 2 unknowns by their physical and chemical properties. Always follow the lab instructor’s directions for wearing goggles and gloves and for proper disposal of excess or used chemicals. Naming and Structure: 1. Alcohols: The hydroxyl (-OH) is the functional group which defines an alcohol. The location of the hydroxyl group is indicated by the number of the carbon to which it is attached. The name suffix becomes –ol for alcohol. Example: 2-Pentanol CH3CHOHCH2CH2CH3 Draw its structure.

There are general locations within an alkane can be identified by primary (1o), secondary (2o), and tertiary (3o). Take 2-methybutane as an example. Draw this molecule. Carbons #1, #4, and the methyl branch are primary (they are attached to only one other carbon.). Carbon #3 is secondary (it is attached to 2 other carbons.) Carbon #2 is tertiary. Why?

Draw and name an example of each primary, secondary, and tertiary alcohols for 2methylbutane.

2. Phenols: Phenols are a special subset of alcohols. They have a hydroxyl group attached to a benzene ring. This allows some of the delocalized pi bond sharing to affect the behavior of the alcohol. The loss of a proton (H+) from the hydroxyl group can be stabilized by resonance with the benzene ring. Example: o-Cresol C6H4OHCH3 Draw its structure.

3. Aldehydes: The carbonyl (C=O) is the functional group present in both aldehydes and ketones. If the carbonyl is at the end of a carbon chain, it is an aldehyde. This makes the location of the carbonyl always carbon #1, so it is not necessary to include a locator number in the name. The name suffix becomes –al for aldehyde. Example: Hexanal CHO(CH2)4CH3 Draw its structure.

4. Ketones: Ketones have a carbonyl on an interior carbon (not at the end of a chain). This position is indicated by the number of the carbon. The name suffix becomes –one for ketone. Methyl ketones have the carbonyl on carbon #2. Example: 3-Pentanone CH3CH2COCH2CH3 Draw its structure.

Physical Properties: 1. Odor: Use the ‘wafting’ method to smell each of the compounds. Record your observations of each in the Table below. 2. Aqueous solubility: Test the solubility of each compound by mixing 10 drops of each in 2 mL water and shake vigorously. Record the results in the Table below. The presence of an oxygen (as a hydroxyl or carbonyl) in what would otherwise be non-polar hydrocarbons changes the everything. Since water is polar, it mixes with other polar substances. These molecules have both polar and non-polar regions in their structures. As the molecules get larger (more carbons), they tend to be less soluble in water. 3. pH: Test the pH of each compounds with pH paper. Record the results in the Table below. The pH scale measures acidity. Neutral is pH 7. Below 7 is acidic and above 7 is basic. Acids can donate a proton, H+.

Physical Properties Data: Odor Ethanol

2-Propanol

t-Butyl alc.

Cyclohexanol

o-Cresol

Propanal

Propanone (acetone)

Cyclohexanone

Unknown Letter _______ Unknown # _________

Aqueous solubility

pH

1.

2.

Chemical Reactions: Chromic acid: Prepare 6 test tubes. Mix 8 drops of each alcohol including the unknown with 2 drops of the chromic acid solution. Record the results in the Table below Chromic acid is a strong oxidizing agent. It reacts with both primary and secondary alcohols. Two hydrogen are lost and the number of bonds to oxygen are increased. Primary alcohols become aldehydes which in turn react to form carboxylic acids. Secondary alcohols are changed into ketones. Tertiary alcohols, phenol, and ketones do not have a set of hydrogen to lose. They do not react. Examples: Primary (1o) alcohol: 1-Butanol CH3CH2CH2CH2OH + H2CrO4 (orange)  CH3CH2CH2CO2H + Cr3+ (green) carboxylic acid Secondary (2o) alcohol: 2-butanol CH3CH2OHCH2CH3 + H2CrO4 (orange)  CH3COCH2CH3 + Cr3+ (green) ketone Aldehyde: Ethanal CH3CHO + H2CrO4 (orange)  CH3CO2H + Cr3+ (green) Iron(III) chloride test: Prepare 6 test tubes. Mix 5 drops of each compound to be tested with 5 drops of 1% FeCl3 solution. Record observations in the Table below. The Iron(III) ion is electron deficient and is attracted to the electron dense pi system of the phenol.

-

Phenol + Fe3+ (yellow)  Phenol Fe3+ Complex (purple) Chemical Reactions: Alcohols: Ethanol 2-Propanol Reaction Type 1. Chromic acid test Observations: Is this what you predicted?

t-Butyl alcohol

Cyclohexanol

o-Cresol

FeCl3 test Observations

Primary, secondary, tertiary, or aromatic? Unknown Letter _______ is ____________________________ because:

Unknown _____

3. Iodoform test: In separate test tubes, mix 20 drops of each aldehyde or ketone plus the unknown with 20 drops of 10% NaOH solution. Warm the mixtures to 60oC. Mix in 40 drops of the iodine reagent. Record the results in the Table below. Methyl ketones have a special reaction with iodine in basic conditions. The iodine atoms replace the hydrogen on the single carbon adjacent to the carbonyl group (carbon #1). This carbon then breaks away from the ketone and forms a bright yellow solid, CHI3. Alkanes may react slowly with the halogen iodine (so the brown color may fade) but only the methyl ketones will produce the yellow precipitate. Example: Butanone CH3COCH2CH3 + 3 I2 (brown) + 4 NaOH  CH3CH2CO2Na + CHI3 (s) (yellow) 4. Benedict’s test oxidation: Prepare 3 test tubes. Mix 10 drops of each aldehyde or ketone including the unknown with 2 mL of the Benedict’s reagent (Cu2+). Warm the mixtures to 60oC. Record the results in the Table below. Copper (II) is an oxidizing agent. It will react with the primary carbonyl of aldehydes but not with the secondary carbonyls of ketones. The reaction replaces the primary hydrogen of the aldehyde with a hydroxyl (-OH) group to make a carboxylic acid. The other product is Cu2O which is a red precipitate. Example: Ethanal CH3CHO + Cu2+ (blue)  CH3COOH + Cu2O (s) (red solid) Chemical reactions: Aldehydes and Ketones: (If no reaction occurs, write NR) Propanal Propanone Unknown (acetone) # ______ 3. Iodoform test Observations Product structure

X

4. Benedict’s test Observations Product structure

Unknown # _____ is ________________________ because:

X...