Which reagents could be used to prepare CH3CH2CONHCH2CH3\text{CH}_3\text{CH}_2\text{CONHCH}_2\text{CH}_3CH3CH2CONHCH2CH3?
CH3CH2CONH2+CH3CH2Cl\text{CH}_3\text{CH}_2\text{CONH}_2 + \text{CH}_3\text{CH}_2\text{Cl}CH3CH2CONH2+CH3CH2Cl
(CH3CH2CO)2O+CH3CH2NH2(\text{CH}_3\text{CH}_2\text{CO})_2\text{O} + \text{CH}_3\text{CH}_2\text{NH}_2(CH3CH2CO)2O+CH3CH2NH2
CH3CH2COONa+CH3CH2NH2\text{CH}_3\text{CH}_2\text{COONa} + \text{CH}_3\text{CH}_2\text{NH}_2CH3CH2COONa+CH3CH2NH2
CH3CH2COCH3+CH3CH2NH2\text{CH}_3\text{CH}_2\text{COCH}_3 + \text{CH}_3\text{CH}_2\text{NH}_2CH3CH2COCH3+CH3CH2NH2