Problem 53 - A Complete Resource Book in Chemistry for JEE Main

Question

Which dye is obtained from plants? (a) indigo (b) orange-I (c) aniline yellow (d) none

Step-by-Step Solution

Answer

Indigo is obtained from plants.

Step 1: Identify the context of dyes

Different dyes have different sources. Some are derived from plants, others from synthetic processes. To find the dye obtained from plants, identify which of the options is associated with natural sources.

Step 2: Analyze each option

Evaluate each option to see its source: (a) Indigo - A naturally occurring dye derived from the indigo plant. (b) Orange-I - A synthetic dye. (c) Aniline Yellow - A synthetic dye derived from aniline. (d) None - This option implies that none of the above are plant-derived.

Step 3: Determine the correct answer

From the analysis, indigo is the only dye that is plant-derived, obtained from the indigo plant. The other options are synthetic dyes.

Key Concepts

Indigo Dye

Indigo dye is a natural dye obtained from the leaves of the indigo plant, scientifically known as *Indigofera tinctoria*. Throughout history, it has been valued for producing a deep and vibrant blue color and has been used in textiles all over the world. The process of extracting indigo dye involves fermenting the plant leaves and then oxidizing the resulting liquid. This ancient dyeing method has been an important cultural and economic staple in many societies.

Indigo's popularity is due to several factors such as:

• Its rich color, which is often associated with luxury and tradition.
• The dye's ability to improve with wash and wear, becoming softer and more appealing over time.
• The versatility it offers for dyeing various natural fibers like cotton, wool, and silk.

Today, indigo dye remains widely used, especially in the fashion industry for denim production. However, most commercially available indigo dye today is synthetically produced, offering a more cost-effective solution for large-scale manufacturing.

Natural Dyes

Natural dyes are derived from natural sources, such as plants, minerals, and even insects. Historically, they have been used in textile coloring before the advent of synthetic dyes. Each natural dye sources its pigment from different components of plants including roots, nuts, bark, and leaves.

There are several key benefits of using natural dyes:

• They are environmentally friendly, as they are biodegradable and less polluting than synthetic dyes.
• Natural dyes are often non-toxic, making them safer for the skin and for the environment.
• They offer a unique spectrum of colors that change based on variables like soil conditions, sun exposure, and harvest methods.

However, natural dyes also have limitations. They can be harder to standardize, leading to inconsistencies in color from batch to batch. Additionally, the range of colors is generally less vibrant than those produced synthetically.

Synthetic Dyes

Synthetic dyes are man-made and have largely replaced natural dyes in the textile industry due to their cost-effectiveness and efficiency. These dyes are created using chemical processes and can produce a tremendous variety of vibrant colors that are consistent and fast to light and washing.

Advantages of synthetic dyes include:

• A broad spectrum of available colors with the ability to create custom shades.
• Consistent results, offering great reliability for mass production.
• Improved colorfastness and durability when compared to some natural dyes.

However, the production and use of synthetic dyes come with environmental concerns. Many synthetic dyes are made from petrochemicals, require substantial water use, and can release harmful byproducts. The push for sustainability has led some manufacturers to reconsider the types and methods of dyes used, balancing vibrant results with ecological impact.