Complete the following reactions: a) CH3CH2C=CCH2CH3 + HCN b) CH3CH2CH2CH2C=CH + HCN

a) The completed chemical reaction is: CH_3CH_2COCH_2CH_3 + HCN \xrightarrow{KCN} \text{CH_3CH_2C(OH)(CN)CH_2CH_3} The IUPAC name for the product is 3-hydroxy-3-cyanopentane.

The chemical mechanism is: Step 1: Nucleophilic attack by cyanide ion. The cyanide ion ($\text{CN}^-$), generated from KCN, acts as a nucleophile and attacks the electrophilic carbon atom of the carbonyl group in 3-pentanone. The $\pi$ electrons of the carbon-oxygen double bond shift to the oxygen atom, forming an alkoxide intermediate. $CH_3CH_2C(=O)CH_2CH_3 + CN^- \longrightarrow CH_3CH_2C(O^-)(CN)CH_2CH_3$

Step 2: Protonation of the alkoxide. The alkoxide intermediate is then protonated by hydrogen cyanide (HCN) to form the stable cyanohydrin product. The cyanide ion is regenerated in this step. $CH_3CH_2C(O^-)(CN)CH_2CH_3 + HCN \longrightarrow CH_3CH_2C(OH)(CN)CH_2CH_3 + CN^-$

b) The completed chemical reaction is: CH_3CH_2CH_2CH_2CHO + HCN \xrightarrow{NaCN} \text{CH_3CH_2CH_2CH_2CH(OH)CN} The IUPAC name for the product is 2-hydroxypentanenitrile.

The chemical mechanism is: Step 1: Nucleophilic attack by cyanide ion. The cyanide ion ($\text{CN}^-$), generated from NaCN, acts as a nucleophile and attacks the electrophilic carbon atom of the carbonyl group in pentanal. The $\pi$ electrons of the carbon-oxygen double bond shift to the oxygen atom, forming an alkoxide intermediate. $CH_3CH_2CH_2CH_2CHO + CN^- \longrightarrow CH_3CH_2CH_2CH_2CH(O^-)CN$

Step 2: Protonation of the alkoxide. The alkoxide intermediate is then protonated by hydrogen cyanide (HCN) to form the stable cyanohydrin product. The cyanide ion is regenerated in this step. $CH_3CH_2CH_2CH_2CH(O^-)CN + HCN \longrightarrow CH_3CH_2CH_2CH_2CH(OH)CN + CN^-$