A compound A derived from isobutanol, soluble in

Let's begin by summarizing the given information: 
- Compound A is derived from isobutanol, has the molecular formula C4H8O2, and reacts with PCl5 and NH3 to give compounds B and C, respectively. 
- Compound B reacts with compound D in the presence of AlCl3 to give compound E with molecular formula C10H12O. 
- Compound C is reduced to compound F with molecular formula C4H11N. 
- Compound F reacts with E in the presence of catalytic amounts of acid to give an aromatic compound G with molecular formula C14H21N.

To determine the structures of these compounds, let's analyze each reaction separately:

Reaction 1: A + PCl5 → B

This is a substitution reaction where PCl5 replaces the -OH group of A with a chlorine atom, forming compound B. The reaction can be represented as:
    CH3     CH3
    |       |
A: CH3 - C - C - OH  + PCl5 →  CH3 - C - C - Cl  (B)
           |  
           CH3

Compound B has the same number of carbons as A (four) and is likely a halogenated alcohol.

Reaction 2: A + NH3 → C

This is a nucleophilic addition reaction where NH3 adds to the carbonyl group of A, forming an imine intermediate which undergoes hydrolysis to give compound C. The reaction can be represented as:
    CH3     CH3
    |       |
A: CH3 - C - C - OH  + NH3 →  CH3 - C - C = NH2  (imine)
           |  
           CH3
                             OH
                         //  
C:  CH3 - C - C = NH2  + H2O →  CH3 - C - C - NH2  (C)
                    |            |
                    CH3         CH3

Compound C has the same number of carbons as A (four) and is likely an amide.

Reaction 3: B + D → E

This is a Friedel-Crafts alkylation reaction where compound B is alkylated by compound D in the presence of AlCl3, forming compound E. The reaction can be represented as:
     CH3     CH3           CH3     CH3
     |       |             |       |
B: CH3 - C - C - Cl  + D →  CH3 - C - C - CH2 - D+  (intermediate)
            |            |  
            CH3          Cl
                             |  
E:   CH3 - C - C - CH2 - D+ + Cl-  →  CH3 - C - C - CH2 - D (E)
                         |              |
                         CH3           CH3

Compound E has twice the number of carbons as B and is likely a substituted biphenyl.

Reaction 4: C → F

This is a reduction reaction where the carbonyl group of compound C is reduced to a primary amine group, forming compound F. The reaction can be represented as:
        CH3     CH3
        |       |
C:   CH3 - C - C - NH2  + 2H2 → CH3 - C - C - NH3+ (F)
               |            |
               CH3         CH3

Compound F has the same number of carbons as C (four) and is likely a primary amine.

Reaction 5: F + E → G

This is a condensation reaction where compound F reacts with compound E in the presence of catalytic amounts of acid to form compound G. The reaction can be represented as:
       CH3     CH3                  CH3     CH3
       |       |                    |       |
F:  CH3 - C - C - NH3+  + E  →  CH3 - C - C - CH2 - E
              |               ||  
              CH3             Cl

                  |
G:     CH3     CH3            CH3     CH3
      |       |              |       |
    CH3 - C - C - NH - CH2 - C - C - CH - E
              |        |        |       |
              CH3     CH3      CH3     CH3

Compound G has twice the number of carbons as F and is likely an aromatic compound.

In summary, the structures of the compounds are as follows:

- Compound A: CH3CH2C(O)CH3 (a methyl ketone derived from isobutanol)
- Compound B: CH3CH2C(Cl)(CH3)OH (a chlorinated alcohol)
- Compound C: CH3CH2C(O)NH2 (a primary amide)
- Compound D: CH3CH2CH2CH2Br (a alkyl halide)
- Compound E: (CH3CH2)2C6H3 (a substituted biphenyl)
- Compound F: CH3CH2CH2NH2 (a primary amine)
- Compound G: (CH3CH2)4C4H2NH (a tetrasubstituted benzene)