`X`: `C_6H_{10}O_4`

`X_1`: `\text{CH}_3\text{COONa}`

`X_2`: `\text{HO-CH}_2\text{COONa}`

`X_3`: `\text{CH}_3\text{CH}_2\text{OH}`

`X_5`: `\text{HO-CH}_2\text{COOH}`

PTHH

`(a)`

`CH_3COOCH_2COOC_2H_5 + 2NaOH \rightarrow CH_3COONa + HOCH_2COONa + C_2H_5OH`

`(b)` 

`CH_3COONa + HCl \rightarrow CH_3COOH + NaCl` 

`c)` 

`HOCH_2COONa + HCl \rightarrow HOCH_2COOH + NaCl`

`d)`

$C_2H_5OH + CuO \xrightarrow{t^o} CH_3CHO + Cu + H_2O$

CTCT của X: `CH_3-COO-CH_2-COO-C_2H_5`