Problem 89 - Chemistry Matter and Change

Question

Infer The sugar glucose is sometimes called dextrose because a solution of glucose is known to be dextrorotatory. Analyze the word dextrorotatory, and suggest what the word means.

Step-by-Step Solution

Answer

Dextrorotatory means rotating plane-polarized light to the right.

Step 1: Break Down 'Dextrorotatory'

The word 'dextrorotatory' is composed of two parts: 'dextro' and 'rotatory'. 'Dextro' comes from the Latin word for 'right', while 'rotatory' means to rotate. Thus, 'dextrorotatory' suggests rotation to the right.

Step 2: Contextualize with Scientific Concept

'Dextrorotatory' is used to describe a substance that rotates plane-polarized light to the right, or clockwise, when viewed from the front. This term is common in optical activity studies in chemistry and biology.

Step 3: Apply to the Exercise

In the context of the exercise, since glucose is dextrorotatory, it means that a solution of glucose rotates plane-polarized light to the right. This optical property is why glucose is sometimes referred to as dextrose.

Key Concepts

Dextrorotatory

The term 'dextrorotatory' comes from two words: 'dextro', which means 'right', and 'rotatory', which implies 'to rotate'. In science, particularly in optical activity, a dextrorotatory compound is one that rotates plane-polarized light towards the right or clockwise direction when viewed from a specific viewpoint. This is a characteristic property of certain optically active substances.

It's quite fascinating that substances can affect light in this way. When light passes through a solution of a dextrorotatory compound, like a sugar solution, it will twist in a rightward path. This twist is measured using an instrument called a polarimeter, which can determine the angle of rotation. Optical activity is a crucial aspect in various fields such as chemistry, biology, and even pharmacology.

Glucose

Glucose, a simple sugar, is essential for many living organisms as a primary energy source. Chemically, it is known as C\(_6\)H\(_{12}\)O\(_6\) and exists in several forms, including an optically active form that exhibits dextrorotation.

In solutions, glucose acts as a dextrorotatory compound, meaning it rotates plane-polarized light to the right. This characteristic gives glucose its alternative name, "dextrose". This behavior is not only fascinating for academic study but also critical in manufacturing and nutrition, where distinguishing between different types of sugars is essential.

• In the human body, glucose is vital for cellular respiration, providing energy for various biochemical reactions.
• Industrially, dextrorotatory glucose is used as a sweetener, in food preservatives, and in the preparation of various medicines.

Plane-Polarized Light

Light waves can move in all directions, but plane-polarized light is special because its waves oscillate in just one direction. This kind of light is very useful in the study of optical activity and chiral molecules.

When plane-polarized light passes through certain substances, like glucose, it can rotate either to the right (dextrorotatory) or to the left (levorotatory). This property is what scientists examine when working with optical isomers.

• Plane-polarized light allows scientists to look into the molecular structure of substances.
• The ability of a substance to rotate polarized light helps in identifying its optical isomer, which is important in various scientific and industrial applications.

The instrument used to measure this rotation and determine optical activity is called a polarimeter. By studying how plane-polarized light interacts with molecules, we can learn a lot about the molecular nature of the substance in question.