What is/are true regarding 20 standard amino acid molecules ?

Options

A. They are all chiral and have L - configuration
B. They have very high melting points compared to other organic compounds of comparable molar masses
C. They have very low solubility in diethyl ether
D. They have very high electrical conductivity in aqueous solution

Explanation

To determine which statements are true regarding the 20 standard amino acid molecules, let's analyze the characteristics of these amino acids step by step.

### Step 1: Chirality and Configuration
- **Statement A**: All 20 standard amino acids are chiral and have L-configuration.
- **Analysis**: While most amino acids are chiral, glycine is an exception because it has two hydrogen atoms attached to its alpha carbon, making it achiral. Therefore, this statement is incorrect.

### Step 2: Melting Points
- **Statement B**: Amino acids have very high melting points compared to other organic compounds of comparable molecular mass.
- **Analysis**: Amino acids contain both amino (-NH2) and carboxyl (-COOH) functional groups, which can form hydrogen bonds. This increases their melting points significantly compared to other organic compounds of similar molecular weight. Therefore, this statement is correct.

### Step 3: Solubility in Diethyl Ether
- **Statement C**: Amino acids have very low solubility in diethyl ether.
- **Analysis**: Amino acids are polar molecules due to their ionic and hydrogen bonding capabilities, making them hydrophilic. Diethyl ether is a non-polar solvent, so amino acids will have low solubility in it. Thus, this statement is also correct.

### Step 4: Electrical Conductivity in Aqueous Solution
- **Statement D**: Amino acids have very high electrical conductivity in aqueous solution.
- **Analysis**: When dissolved in water, amino acids can ionize, releasing ions such as -COO⁻ and -NH₃⁺. This ionization allows them to conduct electricity, making this statement correct.

### Conclusion
- **True Statements**:
- Statement B: Amino acids have very high melting points compared to other organic compounds of comparable molecular mass.
- Statement C: Amino acids have very low solubility in diethyl ether.
- Statement D: Amino acids have very high electrical conductivity in aqueous solution.

### Summary of True Statements
- Only Statement A is false; Statements B, C, and D are true regarding the 20 standard amino acids.

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