# Synthesis of **cis-1-phenyl-1-propene from Benzene Let's break down the problem and go step-by-step from benzene to **cis-1-phenyl-1-propene**. --- ## **Target Molecule** - **cis-1-Phenyl-1-propene:** This is a three-carbon chain with a double bond at the 1-position (adjacent to the phenyl group), and both substituents across the double bond are on the same side (cis, or Z). Structure:  *(Ph = phenyl)* --- ## **Stepwise Synthesis** ### **Step 1: Friedel–Crafts Alkylation (or Acylation + Reduction)** **Benzene → 1-Phenylpropan-1-one (Propiophenone)** - **Reagents:** - Propionyl chloride (CH₃CH₂COCl), AlCl₃ - **Product:** - Propiophenone (C₆H₅COCH₂CH₃) ### **Step 2: Reduction to Alcohol** **Propiophenone → 1-Phenyl-1-propanol** - **Reagents:** - NaBH₄ or LiAlH₄ (reduces ketone to secondary alcohol) - **Product:** - 1-Phenyl-1-propanol (C₆H₅CH(OH)CH₂CH₃) ### **Step 3: Dehydration to Alkene (cis-selective)** **1-Phenyl-1-propanol → cis-1-Phenyl-1-propene** - Standard acid-catalyzed dehydration (H₂SO₄) typically gives the more stable **trans**-alkene. - To get **cis (Z)-alkene**, use a **stereoselective method**: - **Convert the alcohol to a good leaving group (e.g., tosylate)** - **Use a strong, non-nucleophilic base (e.g., KOtBu) at low temperature for E2 elimination** - Or, use **Wittig reaction** (see below for alternative). #### **Alternative: Wittig Reaction (More Selective)** - **Propiophenone → cis-Alkene via Wittig** - React the ketone with a Wittig reagent (Ph₃P=CHCH₃) under conditions favoring cis (Z) isomer formation (use unstabilized ylide, low temperature). --- ## **Summary of Steps and Reagents** | Step | Intermediate/Product | Reagent(s) | |------|--------------------------------|---------------------------| | 1 | Propiophenone | CH₃CH₂COCl, AlCl₃ | | 2 | 1-Phenyl-1-propanol | NaBH₄ or LiAlH₄ | | 3 | cis-1-Phenyl-1-propene | 1. Ph₃P=CHCH₃ (Wittig), | | | (cis only) | 2. Low temp, ether solvent| --- ## **Key Notes** - **Friedel–Crafts acylation** avoids polyalkylation and gives a ketone. - **Wittig reaction** with unstabilized ylides is typically cis-selective. - Acid-catalyzed dehydration usually gives a mix or favors trans, so Wittig is preferred for cis selectivity. --- ## **Final Synthesis Outline** 1. **Benzene** ↓ *(CH₃CH₂COCl, AlCl₃)* 2. **Propiophenone** ↓ *(Ph₃P=CHCH₃, ether, low temp)* 3. **cis-1-Phenyl-1-propene** --- ### **Let me know if you want to see the structures or need further explanation on any step!**

# Synchronous Speed of Induction Motor To calculate the synchronous speed of an induction motor, we can use the following formula: \[ N_s = \frac{120 \times f}{P} \] Where: - \(N_s\) = Synchronous speed (in RPM) - \(f\) = Supply frequency (in Hz) - \(P\) = Number of poles ## Given Data - Number of poles \(P = 6\) - Supply frequency \(f = 50 \, \text{Hz}\) ## Calculation 1. Substitute the values into the formula: \[ N_s = \frac{120 \times 50}{6} \] 2. Calculate: \[ N_s = \frac{6000}{6} = 1000 \, \text{RPM} \] ## Conclusion - The synchronous speed of the 6-pole induction motor connected to a 50 Hz supply is **1000 RPM**.